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# Introduction: Why Google C++ Testing Framework? #
_Google C++ Testing Framework_ helps you write better C++ tests.
No matter whether you work on Linux, Windows, or a Mac, if you write C++ code,
Google Test can help you.
So what makes a good test, and how does Google C++ Testing Framework fit in? We believe:
1. Tests should be _independent_ and _repeatable_. It's a pain to debug a test that succeeds or fails as a result of other tests. Google C++ Testing Framework isolates the tests by running each of them on a different object. When a test fails, Google C++ Testing Framework allows you to run it in isolation for quick debugging.
1. Tests should be well _organized_ and reflect the structure of the tested code. Google C++ Testing Framework groups related tests into test cases that can share data and subroutines. This common pattern is easy to recognize and makes tests easy to maintain. Such consistency is especially helpful when people switch projects and start to work on a new code base.
1. Tests should be _portable_ and _reusable_. The open-source community has a lot of code that is platform-neutral, its tests should also be platform-neutral. Google C++ Testing Framework works on different OSes, with different compilers (gcc, MSVC, and others), with or without exceptions, so Google C++ Testing Framework tests can easily work with a variety of configurations. (Note that the current release only contains build scripts for Linux - we are actively working on scripts for other platforms.)
1. When tests fail, they should provide as much _information_ about the problem as possible. Google C++ Testing Framework doesn't stop at the first test failure. Instead, it only stops the current test and continues with the next. You can also set up tests that report non-fatal failures after which the current test continues. Thus, you can detect and fix multiple bugs in a single run-edit-compile cycle.
1. The testing framework should liberate test writers from housekeeping chores and let them focus on the test _content_. Google C++ Testing Framework automatically keeps track of all tests defined, and doesn't require the user to enumerate them in order to run them.
1. Tests should be _fast_. With Google C++ Testing Framework, you can reuse shared resources across tests and pay for the set-up/tear-down only once, without making tests depend on each other.
Since Google C++ Testing Framework is based on the popular xUnit
architecture, you'll feel right at home if you've used JUnit or PyUnit before.
If not, it will take you about 10 minutes to learn the basics and get started.
So let's go!
_Note:_ We sometimes refer to Google C++ Testing Framework informally
as _Google Test_.
# Setting up a New Test Project #
To write a test program using Google Test, you need to compile Google
Test into a library and link your test with it. We provide build
files for some popular build systems (`msvc/` for Visual Studio,
`xcode/` for Mac Xcode, `make/` for GNU make, `codegear/` for Borland
C++ Builder, and the autotools script in the
Google Test root directory). If your build system is not on this
list, you can take a look at `make/Makefile` to learn how Google Test
should be compiled (basically you want to compile `src/gtest-all.cc`
with `GTEST_ROOT` and `GTEST_ROOT/include` in the header search path,
where `GTEST_ROOT` is the Google Test root directory).
Once you are able to compile the Google Test library, you should
create a project or build target for your test program. Make sure you
have `GTEST_ROOT/include` in the header search path so that the
compiler can find `<gtest/gtest.h>` when compiling your test. Set up
your test project to link with the Google Test library (for example,
in Visual Studio, this is done by adding a dependency on
`gtest.vcproj`).
If you still have questions, take a look at how Google Test's own
tests are built and use them as examples.
# Basic Concepts #
When using Google Test, you start by writing _assertions_, which are statements
that check whether a condition is true. An assertion's result can be _success_,
_nonfatal failure_, or _fatal failure_. If a fatal failure occurs, it aborts
the current function; otherwise the program continues normally.
_Tests_ use assertions to verify the tested code's behavior. If a test crashes
or has a failed assertion, then it _fails_; otherwise it _succeeds_.
A _test case_ contains one or many tests. You should group your tests into test
cases that reflect the structure of the tested code. When multiple tests in a
test case need to share common objects and subroutines, you can put them into a
_test fixture_ class.
A _test program_ can contain multiple test cases.
We'll now explain how to write a test program, starting at the individual
assertion level and building up to tests and test cases.
# Assertions #
Google Test assertions are macros that resemble function calls. You test a
class or function by making assertions about its behavior. When an assertion
fails, Google Test prints the assertion's source file and line number location,
along with a failure message. You may also supply a custom failure message
which will be appended to Google Test's message.
The assertions come in pairs that test the same thing but have different
effects on the current function. `ASSERT_*` versions generate fatal failures
when they fail, and **abort the current function**. `EXPECT_*` versions generate
nonfatal failures, which don't abort the current function. Usually `EXPECT_*`
are preferred, as they allow more than one failures to be reported in a test.
However, you should use `ASSERT_*` if it doesn't make sense to continue when
the assertion in question fails.
Since a failed `ASSERT_*` returns from the current function immediately,
possibly skipping clean-up code that comes after it, it may cause a space leak.
Depending on the nature of the leak, it may or may not be worth fixing - so
keep this in mind if you get a heap checker error in addition to assertion
errors.
To provide a custom failure message, simply stream it into the macro using the
`<<` operator, or a sequence of such operators. An example:
```
ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
for (int i = 0; i < x.size(); ++i) {
EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
}
```
Anything that can be streamed to an `ostream` can be streamed to an assertion
macro--in particular, C strings and `string` objects. If a wide string
(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
streamed to an assertion, it will be translated to UTF-8 when printed.
## Basic Assertions ##
These assertions do basic true/false condition testing.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_TRUE(`_condition_`)`; | `EXPECT_TRUE(`_condition_`)`; | _condition_ is true |
| `ASSERT_FALSE(`_condition_`)`; | `EXPECT_FALSE(`_condition_`)`; | _condition_ is false |
Remember, when they fail, `ASSERT_*` yields a fatal failure and
returns from the current function, while `EXPECT_*` yields a nonfatal
failure, allowing the function to continue running. In either case, an
assertion failure means its containing test fails.
_Availability_: Linux, Windows, Mac.
## Binary Comparison ##
This section describes assertions that compare two values.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
|`ASSERT_EQ(`_expected_`, `_actual_`);`|`EXPECT_EQ(`_expected_`, `_actual_`);`| _expected_ `==` _actual_ |
|`ASSERT_NE(`_val1_`, `_val2_`);` |`EXPECT_NE(`_val1_`, `_val2_`);` | _val1_ `!=` _val2_ |
|`ASSERT_LT(`_val1_`, `_val2_`);` |`EXPECT_LT(`_val1_`, `_val2_`);` | _val1_ `<` _val2_ |
|`ASSERT_LE(`_val1_`, `_val2_`);` |`EXPECT_LE(`_val1_`, `_val2_`);` | _val1_ `<=` _val2_ |
|`ASSERT_GT(`_val1_`, `_val2_`);` |`EXPECT_GT(`_val1_`, `_val2_`);` | _val1_ `>` _val2_ |
|`ASSERT_GE(`_val1_`, `_val2_`);` |`EXPECT_GE(`_val1_`, `_val2_`);` | _val1_ `>=` _val2_ |
In the event of a failure, Google Test prints both _val1_ and _val2_
. In `ASSERT_EQ*` and `EXPECT_EQ*` (and all other equality assertions
we'll introduce later), you should put the expression you want to test
in the position of _actual_, and put its expected value in _expected_,
as Google Test's failure messages are optimized for this convention.
Value arguments must be comparable by the assertion's comparison operator or
you'll get a compiler error. Values must also support the `<<` operator for
streaming to an `ostream`. All built-in types support this.
These assertions can work with a user-defined type, but only if you define the
corresponding comparison operator (e.g. `==`, `<`, etc). If the corresponding
operator is defined, prefer using the `ASSERT_*()` macros because they will
print out not only the result of the comparison, but the two operands as well.
Arguments are always evaluated exactly once. Therefore, it's OK for the
arguments to have side effects. However, as with any ordinary C/C++ function,
the arguments' evaluation order is undefined (i.e. the compiler is free to
choose any order) and your code should not depend on any particular argument
evaluation order.
`ASSERT_EQ()` does pointer equality on pointers. If used on two C strings, it
tests if they are in the same memory location, not if they have the same value.
Therefore, if you want to compare C strings (e.g. `const char*`) by value, use
`ASSERT_STREQ()` , which will be described later on. In particular, to assert
that a C string is `NULL`, use `ASSERT_STREQ(NULL, c_string)` . However, to
compare two `string` objects, you should use `ASSERT_EQ`.
Macros in this section work with both narrow and wide string objects (`string`
and `wstring`).
_Availability_: Linux, Windows, Mac.
## String Comparison ##
The assertions in this group compare two **C strings**. If you want to compare
two `string` objects, use `EXPECT_EQ`, `EXPECT_NE`, and etc instead.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_STREQ(`_expected\_str_`, `_actual\_str_`);` | `EXPECT_STREQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content |
| `ASSERT_STRNE(`_str1_`, `_str2_`);` | `EXPECT_STRNE(`_str1_`, `_str2_`);` | the two C strings have different content |
| `ASSERT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);`| `EXPECT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content, ignoring case |
| `ASSERT_STRCASENE(`_str1_`, `_str2_`);`| `EXPECT_STRCASENE(`_str1_`, `_str2_`);` | the two C strings have different content, ignoring case |
Note that "CASE" in an assertion name means that case is ignored.
`*STREQ*` and `*STRNE*` also accept wide C strings (`wchar_t*`). If a
comparison of two wide strings fails, their values will be printed as UTF-8
narrow strings.
A `NULL` pointer and an empty string are considered _different_.
_Availability_: Linux, Windows, Mac.
See also: For more string comparison tricks (substring, prefix, suffix, and
regular expression matching, for example), see the [AdvancedGuide Advanced
Google Test Guide].
# Simple Tests #
To create a test:
1. Use the `TEST()` macro to define and name a test function, These are ordinary C++ functions that don't return a value.
1. In this function, along with any valid C++ statements you want to include, use the various Google Test assertions to check values.
1. The test's result is determined by the assertions; if any assertion in the test fails (either fatally or non-fatally), or if the test crashes, the entire test fails. Otherwise, it succeeds.
```
TEST(test_case_name, test_name) {
... test body ...
}
```
`TEST()` arguments go from general to specific. The _first_ argument is the
name of the test case, and the _second_ argument is the test's name within the
test case. Remember that a test case can contain any number of individual
tests. A test's _full name_ consists of its containing test case and its
individual name. Tests from different test cases can have the same individual
name.
For example, let's take a simple integer function:
```
int Factorial(int n); // Returns the factorial of n
```
A test case for this function might look like:
```
// Tests factorial of 0.
TEST(FactorialTest, HandlesZeroInput) {
EXPECT_EQ(1, Factorial(0));
}
// Tests factorial of positive numbers.
TEST(FactorialTest, HandlesPositiveInput) {
EXPECT_EQ(1, Factorial(1));
EXPECT_EQ(2, Factorial(2));
EXPECT_EQ(6, Factorial(3));
EXPECT_EQ(40320, Factorial(8));
}
```
Google Test groups the test results by test cases, so logically-related tests
should be in the same test case; in other words, the first argument to their
`TEST()` should be the same. In the above example, we have two tests,
`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
case `FactorialTest`.
_Availability_: Linux, Windows, Mac.
# Test Fixtures: Using the Same Data Configuration for Multiple Tests #
If you find yourself writing two or more tests that operate on similar data,
you can use a _test fixture_. It allows you to reuse the same configuration of
objects for several different tests.
To create a fixture, just:
1. Derive a class from `::testing::Test` . Start its body with `protected:` or `public:` as we'll want to access fixture members from sub-classes.
1. Inside the class, declare any objects you plan to use.
1. If necessary, write a default constructor or `SetUp()` function to prepare the objects for each test. A common mistake is to spell `SetUp()` as `Setup()` with a small `u` - don't let that happen to you.
1. If necessary, write a destructor or `TearDown()` function to release any resources you allocated in `SetUp()` . To learn when you should use the constructor/destructor and when you should use `SetUp()/TearDown()`, read this [FAQ entry](V1_5_FAQ.md#should-i-use-the-constructordestructor-of-the-test-fixture-or-the-set-uptear-down-function).
1. If needed, define subroutines for your tests to share.
When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
access objects and subroutines in the test fixture:
```
TEST_F(test_case_name, test_name) {
... test body ...
}
```
Like `TEST()`, the first argument is the test case name, but for `TEST_F()`
this must be the name of the test fixture class. You've probably guessed: `_F`
is for fixture.
Unfortunately, the C++ macro system does not allow us to create a single macro
that can handle both types of tests. Using the wrong macro causes a compiler
error.
Also, you must first define a test fixture class before using it in a
`TEST_F()`, or you'll get the compiler error "`virtual outside class
declaration`".
For each test defined with `TEST_F()`, Google Test will:
1. Create a _fresh_ test fixture at runtime
1. Immediately initialize it via `SetUp()` ,
1. Run the test
1. Clean up by calling `TearDown()`
1. Delete the test fixture. Note that different tests in the same test case have different test fixture objects, and Google Test always deletes a test fixture before it creates the next one. Google Test does not reuse the same test fixture for multiple tests. Any changes one test makes to the fixture do not affect other tests.
As an example, let's write tests for a FIFO queue class named `Queue`, which
has the following interface:
```
template <typename E> // E is the element type.
class Queue {
public:
Queue();
void Enqueue(const E& element);
E* Dequeue(); // Returns NULL if the queue is empty.
size_t size() const;
...
};
```
First, define a fixture class. By convention, you should give it the name
`FooTest` where `Foo` is the class being tested.
```
class QueueTest : public ::testing::Test {
protected:
virtual void SetUp() {
q1_.Enqueue(1);
q2_.Enqueue(2);
q2_.Enqueue(3);
}
// virtual void TearDown() {}
Queue<int> q0_;
Queue<int> q1_;
Queue<int> q2_;
};
```
In this case, `TearDown()` is not needed since we don't have to clean up after
each test, other than what's already done by the destructor.
Now we'll write tests using `TEST_F()` and this fixture.
```
TEST_F(QueueTest, IsEmptyInitially) {
EXPECT_EQ(0, q0_.size());
}
TEST_F(QueueTest, DequeueWorks) {
int* n = q0_.Dequeue();
EXPECT_EQ(NULL, n);
n = q1_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(1, *n);
EXPECT_EQ(0, q1_.size());
delete n;
n = q2_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(2, *n);
EXPECT_EQ(1, q2_.size());
delete n;
}
```
The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
to use `EXPECT_*` when you want the test to continue to reveal more errors
after the assertion failure, and use `ASSERT_*` when continuing after failure
doesn't make sense. For example, the second assertion in the `Dequeue` test is
`ASSERT_TRUE(n != NULL)`, as we need to dereference the pointer `n` later,
which would lead to a segfault when `n` is `NULL`.
When these tests run, the following happens:
1. Google Test constructs a `QueueTest` object (let's call it `t1` ).
1. `t1.SetUp()` initializes `t1` .
1. The first test ( `IsEmptyInitially` ) runs on `t1` .
1. `t1.TearDown()` cleans up after the test finishes.
1. `t1` is destructed.
1. The above steps are repeated on another `QueueTest` object, this time running the `DequeueWorks` test.
_Availability_: Linux, Windows, Mac.
_Note_: Google Test automatically saves all _Google Test_ flags when a test
object is constructed, and restores them when it is destructed.
# Invoking the Tests #
`TEST()` and `TEST_F()` implicitly register their tests with Google Test. So, unlike with many other C++ testing frameworks, you don't have to re-list all your defined tests in order to run them.
After defining your tests, you can run them with `RUN_ALL_TESTS()` , which returns `0` if all the tests are successful, or `1` otherwise. Note that `RUN_ALL_TESTS()` runs _all tests_ in your link unit -- they can be from different test cases, or even different source files.
When invoked, the `RUN_ALL_TESTS()` macro:
1. Saves the state of all Google Test flags.
1. Creates a test fixture object for the first test.
1. Initializes it via `SetUp()`.
1. Runs the test on the fixture object.
1. Cleans up the fixture via `TearDown()`.
1. Deletes the fixture.
1. Restores the state of all Google Test flags.
1. Repeats the above steps for the next test, until all tests have run.
In addition, if the text fixture's constructor generates a fatal failure in
step 2, there is no point for step 3 - 5 and they are thus skipped. Similarly,
if step 3 generates a fatal failure, step 4 will be skipped.
_Important_: You must not ignore the return value of `RUN_ALL_TESTS()`, or `gcc`
will give you a compiler error. The rationale for this design is that the
automated testing service determines whether a test has passed based on its
exit code, not on its stdout/stderr output; thus your `main()` function must
return the value of `RUN_ALL_TESTS()`.
Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than once
conflicts with some advanced Google Test features (e.g. thread-safe death
tests) and thus is not supported.
_Availability_: Linux, Windows, Mac.
# Writing the main() Function #
You can start from this boilerplate:
```
#include "this/package/foo.h"
#include <gtest/gtest.h>
namespace {
// The fixture for testing class Foo.
class FooTest : public ::testing::Test {
protected:
// You can remove any or all of the following functions if its body
// is empty.
FooTest() {
// You can do set-up work for each test here.
}
virtual ~FooTest() {
// You can do clean-up work that doesn't throw exceptions here.
}
// If the constructor and destructor are not enough for setting up
// and cleaning up each test, you can define the following methods:
virtual void SetUp() {
// Code here will be called immediately after the constructor (right
// before each test).
}
virtual void TearDown() {
// Code here will be called immediately after each test (right
// before the destructor).
}
// Objects declared here can be used by all tests in the test case for Foo.
};
// Tests that the Foo::Bar() method does Abc.
TEST_F(FooTest, MethodBarDoesAbc) {
const string input_filepath = "this/package/testdata/myinputfile.dat";
const string output_filepath = "this/package/testdata/myoutputfile.dat";
Foo f;
EXPECT_EQ(0, f.Bar(input_filepath, output_filepath));
}
// Tests that Foo does Xyz.
TEST_F(FooTest, DoesXyz) {
// Exercises the Xyz feature of Foo.
}
} // namespace
int main(int argc, char **argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
The `::testing::InitGoogleTest()` function parses the command line for Google
Test flags, and removes all recognized flags. This allows the user to control a
test program's behavior via various flags, which we'll cover in [AdvancedGuide](V1_5_AdvancedGuide.md).
You must call this function before calling `RUN_ALL_TESTS()`, or the flags
won't be properly initialized.
On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
in programs compiled in `UNICODE` mode as well.
But maybe you think that writing all those main() functions is too much work? We agree with you completely and that's why Google Test provides a basic implementation of main(). If it fits your needs, then just link your test with gtest\_main library and you are good to go.
## Important note for Visual C++ users ##
If you put your tests into a library and your `main()` function is in a different library or in your .exe file, those tests will not run. The reason is a [bug](https://connect.microsoft.com/feedback/viewfeedback.aspx?FeedbackID=244410&siteid=210) in Visual C++. When you define your tests, Google Test creates certain static objects to register them. These objects are not referenced from elsewhere but their constructors are still supposed to run. When Visual C++ linker sees that nothing in the library is referenced from other places it throws the library out. You have to reference your library with tests from your main program to keep the linker from discarding it. Here is how to do it. Somewhere in your library code declare a function:
```
__declspec(dllexport) int PullInMyLibrary() { return 0; }
```
If you put your tests in a static library (not DLL) then `__declspec(dllexport)` is not required. Now, in your main program, write a code that invokes that function:
```
int PullInMyLibrary();
static int dummy = PullInMyLibrary();
```
This will keep your tests referenced and will make them register themselves at startup.
In addition, if you define your tests in a static library, add `/OPT:NOREF` to your main program linker options. If you use MSVC++ IDE, go to your .exe project properties/Configuration Properties/Linker/Optimization and set References setting to `Keep Unreferenced Data (/OPT:NOREF)`. This will keep Visual C++ linker from discarding individual symbols generated by your tests from the final executable.
There is one more pitfall, though. If you use Google Test as a static library (that's how it is defined in gtest.vcproj) your tests must also reside in a static library. If you have to have them in a DLL, you _must_ change Google Test to build into a DLL as well. Otherwise your tests will not run correctly or will not run at all. The general conclusion here is: make your life easier - do not write your tests in libraries!
# Where to Go from Here #
Congratulations! You've learned the Google Test basics. You can start writing
and running Google Test tests, read some [samples](Samples.md), or continue with
[AdvancedGuide](V1_5_AdvancedGuide.md), which describes many more useful Google Test features.
# Known Limitations #
Google Test is designed to be thread-safe. The implementation is
thread-safe on systems where the `pthreads` library is available. It
is currently _unsafe_ to use Google Test assertions from two threads
concurrently on other systems (e.g. Windows). In most tests this is
not an issue as usually the assertions are done in the main thread. If
you want to help, you can volunteer to implement the necessary
synchronization primitives in `gtest-port.h` for your platform.
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<b>P</b>ump is <b>U</b>seful for <b>M</b>eta <b>P</b>rogramming.
# The Problem #
Template and macro libraries often need to define many classes,
functions, or macros that vary only (or almost only) in the number of
arguments they take. It's a lot of repetitive, mechanical, and
error-prone work.
Variadic templates and variadic macros can alleviate the problem.
However, while both are being considered by the C++ committee, neither
is in the standard yet or widely supported by compilers. Thus they
are often not a good choice, especially when your code needs to be
portable. And their capabilities are still limited.
As a result, authors of such libraries often have to write scripts to
generate their implementation. However, our experience is that it's
tedious to write such scripts, which tend to reflect the structure of
the generated code poorly and are often hard to read and edit. For
example, a small change needed in the generated code may require some
non-intuitive, non-trivial changes in the script. This is especially
painful when experimenting with the code.
# Our Solution #
Pump (for Pump is Useful for Meta Programming, Pretty Useful for Meta
Programming, or Practical Utility for Meta Programming, whichever you
prefer) is a simple meta-programming tool for C++. The idea is that a
programmer writes a `foo.pump` file which contains C++ code plus meta
code that manipulates the C++ code. The meta code can handle
iterations over a range, nested iterations, local meta variable
definitions, simple arithmetic, and conditional expressions. You can
view it as a small Domain-Specific Language. The meta language is
designed to be non-intrusive (s.t. it won't confuse Emacs' C++ mode,
for example) and concise, making Pump code intuitive and easy to
maintain.
## Highlights ##
* The implementation is in a single Python script and thus ultra portable: no build or installation is needed and it works cross platforms.
* Pump tries to be smart with respect to [Google's style guide](http://code.google.com/p/google-styleguide/): it breaks long lines (easy to have when they are generated) at acceptable places to fit within 80 columns and indent the continuation lines correctly.
* The format is human-readable and more concise than XML.
* The format works relatively well with Emacs' C++ mode.
## Examples ##
The following Pump code (where meta keywords start with `$`, `[[` and `]]` are meta brackets, and `$$` starts a meta comment that ends with the line):
```
$var n = 3 $$ Defines a meta variable n.
$range i 0..n $$ Declares the range of meta iterator i (inclusive).
$for i [[
$$ Meta loop.
// Foo$i does blah for $i-ary predicates.
$range j 1..i
template <size_t N $for j [[, typename A$j]]>
class Foo$i {
$if i == 0 [[
blah a;
]] $elif i <= 2 [[
blah b;
]] $else [[
blah c;
]]
};
]]
```
will be translated by the Pump compiler to:
```
// Foo0 does blah for 0-ary predicates.
template <size_t N>
class Foo0 {
blah a;
};
// Foo1 does blah for 1-ary predicates.
template <size_t N, typename A1>
class Foo1 {
blah b;
};
// Foo2 does blah for 2-ary predicates.
template <size_t N, typename A1, typename A2>
class Foo2 {
blah b;
};
// Foo3 does blah for 3-ary predicates.
template <size_t N, typename A1, typename A2, typename A3>
class Foo3 {
blah c;
};
```
In another example,
```
$range i 1..n
Func($for i + [[a$i]]);
$$ The text between i and [[ is the separator between iterations.
```
will generate one of the following lines (without the comments), depending on the value of `n`:
```
Func(); // If n is 0.
Func(a1); // If n is 1.
Func(a1 + a2); // If n is 2.
Func(a1 + a2 + a3); // If n is 3.
// And so on...
```
## Constructs ##
We support the following meta programming constructs:
| `$var id = exp` | Defines a named constant value. `$id` is valid util the end of the current meta lexical block. |
|:----------------|:-----------------------------------------------------------------------------------------------|
| $range id exp..exp | Sets the range of an iteration variable, which can be reused in multiple loops later. |
| $for id sep [[code ](.md)] | Iteration. The range of `id` must have been defined earlier. `$id` is valid in `code`. |
| `$($)` | Generates a single `$` character. |
| `$id` | Value of the named constant or iteration variable. |
| `$(exp)` | Value of the expression. |
| `$if exp [[ code ]] else_branch` | Conditional. |
| `[[ code ]]` | Meta lexical block. |
| `cpp_code` | Raw C++ code. |
| `$$ comment` | Meta comment. |
**Note:** To give the user some freedom in formatting the Pump source
code, Pump ignores a new-line character if it's right after `$for foo`
or next to `[[` or `]]`. Without this rule you'll often be forced to write
very long lines to get the desired output. Therefore sometimes you may
need to insert an extra new-line in such places for a new-line to show
up in your output.
## Grammar ##
```
code ::= atomic_code*
atomic_code ::= $var id = exp
| $var id = [[ code ]]
| $range id exp..exp
| $for id sep [[ code ]]
| $($)
| $id
| $(exp)
| $if exp [[ code ]] else_branch
| [[ code ]]
| cpp_code
sep ::= cpp_code | empty_string
else_branch ::= $else [[ code ]]
| $elif exp [[ code ]] else_branch
| empty_string
exp ::= simple_expression_in_Python_syntax
```
## Code ##
You can find the source code of Pump in [scripts/pump.py](http://code.google.com/p/googletest/source/browse/trunk/scripts/pump.py). It is still
very unpolished and lacks automated tests, although it has been
successfully used many times. If you find a chance to use it in your
project, please let us know what you think! We also welcome help on
improving Pump.
## Real Examples ##
You can find real-world applications of Pump in [Google Test](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgoogletest\.googlecode\.com) and [Google Mock](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgooglemock\.googlecode\.com). The source file `foo.h.pump` generates `foo.h`.
## Tips ##
* If a meta variable is followed by a letter or digit, you can separate them using `[[]]`, which inserts an empty string. For example `Foo$j[[]]Helper` generate `Foo1Helper` when `j` is 1.
* To avoid extra-long Pump source lines, you can break a line anywhere you want by inserting `[[]]` followed by a new line. Since any new-line character next to `[[` or `]]` is ignored, the generated code won't contain this new line.
\ No newline at end of file
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This guide will explain how to use the Google Testing Framework in your Xcode projects on Mac OS X. This tutorial begins by quickly explaining what to do for experienced users. After the quick start, the guide goes provides additional explanation about each step.
# Quick Start #
Here is the quick guide for using Google Test in your Xcode project.
1. Download the source from the [website](http://code.google.com/p/googletest) using this command: `svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only`
1. Open up the `gtest.xcodeproj` in the `googletest-read-only/xcode/` directory and build the gtest.framework.
1. Create a new "Shell Tool" target in your Xcode project called something like "UnitTests"
1. Add the gtest.framework to your project and add it to the "Link Binary with Libraries" build phase of "UnitTests"
1. Add your unit test source code to the "Compile Sources" build phase of "UnitTests"
1. Edit the "UnitTests" executable and add an environment variable named "DYLD\_FRAMEWORK\_PATH" with a value equal to the path to the framework containing the gtest.framework relative to the compiled executable.
1. Build and Go
The following sections further explain each of the steps listed above in depth, describing in more detail how to complete it including some variations.
# Get the Source #
Currently, the gtest.framework discussed here isn't available in a tagged release of Google Test, it is only available in the trunk. As explained at the Google Test [site](http://code.google.com/p/googletest/source/checkout">svn), you can get the code from anonymous SVN with this command:
```
svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only
```
Alternatively, if you are working with Subversion in your own code base, you can add Google Test as an external dependency to your own Subversion repository. By following this approach, everyone that checks out your svn repository will also receive a copy of Google Test (a specific version, if you wish) without having to check it out explicitly. This makes the set up of your project simpler and reduces the copied code in the repository.
To use `svn:externals`, decide where you would like to have the external source reside. You might choose to put the external source inside the trunk, because you want it to be part of the branch when you make a release. However, keeping it outside the trunk in a version-tagged directory called something like `third-party/googletest/1.0.1`, is another option. Once the location is established, use `svn propedit svn:externals _directory_` to set the svn:externals property on a directory in your repository. This directory won't contain the code, but be its versioned parent directory.
The command `svn propedit` will bring up your Subversion editor, making editing the long, (potentially multi-line) property simpler. This same method can be used to check out a tagged branch, by using the appropriate URL (e.g. `http://googletest.googlecode.com/svn/tags/release-1.0.1`). Additionally, the svn:externals property allows the specification of a particular revision of the trunk with the `-r_##_` option (e.g. `externals/src/googletest -r60 http://googletest.googlecode.com/svn/trunk`).
Here is an example of using the svn:externals properties on a trunk (read via `svn propget`) of a project. This value checks out a copy of Google Test into the `trunk/externals/src/googletest/` directory.
```
[Computer:svn] user$ svn propget svn:externals trunk
externals/src/googletest http://googletest.googlecode.com/svn/trunk
```
# Add the Framework to Your Project #
The next step is to build and add the gtest.framework to your own project. This guide describes two common ways below.
* **Option 1** --- The simplest way to add Google Test to your own project, is to open gtest.xcodeproj (found in the xcode/ directory of the Google Test trunk) and build the framework manually. Then, add the built framework into your project using the "Add->Existing Framework..." from the context menu or "Project->Add..." from the main menu. The gtest.framework is relocatable and contains the headers and object code that you'll need to make tests. This method requires rebuilding every time you upgrade Google Test in your project.
* **Option 2** --- If you are going to be living off the trunk of Google Test, incorporating its latest features into your unit tests (or are a Google Test developer yourself). You'll want to rebuild the framework every time the source updates. to do this, you'll need to add the gtest.xcodeproj file, not the framework itself, to your own Xcode project. Then, from the build products that are revealed by the project's disclosure triangle, you can find the gtest.framework, which can be added to your targets (discussed below).
# Make a Test Target #
To start writing tests, make a new "Shell Tool" target. This target template is available under BSD, Cocoa, or Carbon. Add your unit test source code to the "Compile Sources" build phase of the target.
Next, you'll want to add gtest.framework in two different ways, depending upon which option you chose above.
* **Option 1** --- During compilation, Xcode will need to know that you are linking against the gtest.framework. Add the gtest.framework to the "Link Binary with Libraries" build phase of your test target. This will include the Google Test headers in your header search path, and will tell the linker where to find the library.
* **Option 2** --- If your working out of the trunk, you'll also want to add gtest.framework to your "Link Binary with Libraries" build phase of your test target. In addition, you'll want to add the gtest.framework as a dependency to your unit test target. This way, Xcode will make sure that gtest.framework is up to date, every time your build your target. Finally, if you don't share build directories with Google Test, you'll have to copy the gtest.framework into your own build products directory using a "Run Script" build phase.
# Set Up the Executable Run Environment #
Since the unit test executable is a shell tool, it doesn't have a bundle with a `Contents/Frameworks` directory, in which to place gtest.framework. Instead, the dynamic linker must be told at runtime to search for the framework in another location. This can be accomplished by setting the "DYLD\_FRAMEWORK\_PATH" environment variable in the "Edit Active Executable ..." Arguments tab, under "Variables to be set in the environment:". The path for this value is the path (relative or absolute) of the directory containing the gtest.framework.
If you haven't set up the DYLD\_FRAMEWORK\_PATH, correctly, you might get a message like this:
```
[Session started at 2008-08-15 06:23:57 -0600.]
dyld: Library not loaded: @loader_path/../Frameworks/gtest.framework/Versions/A/gtest
Referenced from: /Users/username/Documents/Sandbox/gtestSample/build/Debug/WidgetFrameworkTest
Reason: image not found
```
To correct this problem, got to the directory containing the executable named in "Referenced from:" value in the error message above. Then, with the terminal in this location, find the relative path to the directory containing the gtest.framework. That is the value you'll need to set as the DYLD\_FRAMEWORK\_PATH.
# Build and Go #
Now, when you click "Build and Go", the test will be executed. Dumping out something like this:
```
[Session started at 2008-08-06 06:36:13 -0600.]
[==========] Running 2 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 2 tests from WidgetInitializerTest
[ RUN ] WidgetInitializerTest.TestConstructor
[ OK ] WidgetInitializerTest.TestConstructor
[ RUN ] WidgetInitializerTest.TestConversion
[ OK ] WidgetInitializerTest.TestConversion
[----------] Global test environment tear-down
[==========] 2 tests from 1 test case ran.
[ PASSED ] 2 tests.
The Debugger has exited with status 0.
```
# Summary #
Unit testing is a valuable way to ensure your data model stays valid even during rapid development or refactoring. The Google Testing Framework is a great unit testing framework for C and C++ which integrates well with an Xcode development environment.
\ No newline at end of file
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Now that you have read [Primer](V1_6_Primer.md) and learned how to write tests
using Google Test, it's time to learn some new tricks. This document
will show you more assertions as well as how to construct complex
failure messages, propagate fatal failures, reuse and speed up your
test fixtures, and use various flags with your tests.
# More Assertions #
This section covers some less frequently used, but still significant,
assertions.
## Explicit Success and Failure ##
These three assertions do not actually test a value or expression. Instead,
they generate a success or failure directly. Like the macros that actually
perform a test, you may stream a custom failure message into the them.
| `SUCCEED();` |
|:-------------|
Generates a success. This does NOT make the overall test succeed. A test is
considered successful only if none of its assertions fail during its execution.
Note: `SUCCEED()` is purely documentary and currently doesn't generate any
user-visible output. However, we may add `SUCCEED()` messages to Google Test's
output in the future.
| `FAIL();` | `ADD_FAILURE();` | `ADD_FAILURE_AT("`_file\_path_`", `_line\_number_`);` |
|:-----------|:-----------------|:------------------------------------------------------|
`FAIL()` generates a fatal failure, while `ADD_FAILURE()` and `ADD_FAILURE_AT()` generate a nonfatal
failure. These are useful when control flow, rather than a Boolean expression,
deteremines the test's success or failure. For example, you might want to write
something like:
```
switch(expression) {
case 1: ... some checks ...
case 2: ... some other checks
...
default: FAIL() << "We shouldn't get here.";
}
```
_Availability_: Linux, Windows, Mac.
## Exception Assertions ##
These are for verifying that a piece of code throws (or does not
throw) an exception of the given type:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_THROW(`_statement_, _exception\_type_`);` | `EXPECT_THROW(`_statement_, _exception\_type_`);` | _statement_ throws an exception of the given type |
| `ASSERT_ANY_THROW(`_statement_`);` | `EXPECT_ANY_THROW(`_statement_`);` | _statement_ throws an exception of any type |
| `ASSERT_NO_THROW(`_statement_`);` | `EXPECT_NO_THROW(`_statement_`);` | _statement_ doesn't throw any exception |
Examples:
```
ASSERT_THROW(Foo(5), bar_exception);
EXPECT_NO_THROW({
int n = 5;
Bar(&n);
});
```
_Availability_: Linux, Windows, Mac; since version 1.1.0.
## Predicate Assertions for Better Error Messages ##
Even though Google Test has a rich set of assertions, they can never be
complete, as it's impossible (nor a good idea) to anticipate all the scenarios
a user might run into. Therefore, sometimes a user has to use `EXPECT_TRUE()`
to check a complex expression, for lack of a better macro. This has the problem
of not showing you the values of the parts of the expression, making it hard to
understand what went wrong. As a workaround, some users choose to construct the
failure message by themselves, streaming it into `EXPECT_TRUE()`. However, this
is awkward especially when the expression has side-effects or is expensive to
evaluate.
Google Test gives you three different options to solve this problem:
### Using an Existing Boolean Function ###
If you already have a function or a functor that returns `bool` (or a type
that can be implicitly converted to `bool`), you can use it in a _predicate
assertion_ to get the function arguments printed for free:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_PRED1(`_pred1, val1_`);` | `EXPECT_PRED1(`_pred1, val1_`);` | _pred1(val1)_ returns true |
| `ASSERT_PRED2(`_pred2, val1, val2_`);` | `EXPECT_PRED2(`_pred2, val1, val2_`);` | _pred2(val1, val2)_ returns true |
| ... | ... | ... |
In the above, _predn_ is an _n_-ary predicate function or functor, where
_val1_, _val2_, ..., and _valn_ are its arguments. The assertion succeeds
if the predicate returns `true` when applied to the given arguments, and fails
otherwise. When the assertion fails, it prints the value of each argument. In
either case, the arguments are evaluated exactly once.
Here's an example. Given
```
// Returns true iff m and n have no common divisors except 1.
bool MutuallyPrime(int m, int n) { ... }
const int a = 3;
const int b = 4;
const int c = 10;
```
the assertion `EXPECT_PRED2(MutuallyPrime, a, b);` will succeed, while the
assertion `EXPECT_PRED2(MutuallyPrime, b, c);` will fail with the message
<pre>
!MutuallyPrime(b, c) is false, where<br>
b is 4<br>
c is 10<br>
</pre>
**Notes:**
1. If you see a compiler error "no matching function to call" when using `ASSERT_PRED*` or `EXPECT_PRED*`, please see [this](v1_6_FAQ.md#ithe-compiler-complains-about-undefined-references-to-some-static-const-member-variables-but-i-did-define-them-in-the-class-body-whats-wrong) for how to resolve it.
1. Currently we only provide predicate assertions of arity <= 5. If you need a higher-arity assertion, let us know.
_Availability_: Linux, Windows, Mac
### Using a Function That Returns an AssertionResult ###
While `EXPECT_PRED*()` and friends are handy for a quick job, the
syntax is not satisfactory: you have to use different macros for
different arities, and it feels more like Lisp than C++. The
`::testing::AssertionResult` class solves this problem.
An `AssertionResult` object represents the result of an assertion
(whether it's a success or a failure, and an associated message). You
can create an `AssertionResult` using one of these factory
functions:
```
namespace testing {
// Returns an AssertionResult object to indicate that an assertion has
// succeeded.
AssertionResult AssertionSuccess();
// Returns an AssertionResult object to indicate that an assertion has
// failed.
AssertionResult AssertionFailure();
}
```
You can then use the `<<` operator to stream messages to the
`AssertionResult` object.
To provide more readable messages in Boolean assertions
(e.g. `EXPECT_TRUE()`), write a predicate function that returns
`AssertionResult` instead of `bool`. For example, if you define
`IsEven()` as:
```
::testing::AssertionResult IsEven(int n) {
if ((n % 2) == 0)
return ::testing::AssertionSuccess();
else
return ::testing::AssertionFailure() << n << " is odd";
}
```
instead of:
```
bool IsEven(int n) {
return (n % 2) == 0;
}
```
the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print:
<pre>
Value of: !IsEven(Fib(4))<br>
Actual: false (*3 is odd*)<br>
Expected: true<br>
</pre>
instead of a more opaque
<pre>
Value of: !IsEven(Fib(4))<br>
Actual: false<br>
Expected: true<br>
</pre>
If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE`
as well, and are fine with making the predicate slower in the success
case, you can supply a success message:
```
::testing::AssertionResult IsEven(int n) {
if ((n % 2) == 0)
return ::testing::AssertionSuccess() << n << " is even";
else
return ::testing::AssertionFailure() << n << " is odd";
}
```
Then the statement `EXPECT_FALSE(IsEven(Fib(6)))` will print
<pre>
Value of: !IsEven(Fib(6))<br>
Actual: true (8 is even)<br>
Expected: false<br>
</pre>
_Availability_: Linux, Windows, Mac; since version 1.4.1.
### Using a Predicate-Formatter ###
If you find the default message generated by `(ASSERT|EXPECT)_PRED*` and
`(ASSERT|EXPECT)_(TRUE|FALSE)` unsatisfactory, or some arguments to your
predicate do not support streaming to `ostream`, you can instead use the
following _predicate-formatter assertions_ to _fully_ customize how the
message is formatted:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_PRED_FORMAT1(`_pred\_format1, val1_`);` | `EXPECT_PRED_FORMAT1(`_pred\_format1, val1_`); | _pred\_format1(val1)_ is successful |
| `ASSERT_PRED_FORMAT2(`_pred\_format2, val1, val2_`);` | `EXPECT_PRED_FORMAT2(`_pred\_format2, val1, val2_`);` | _pred\_format2(val1, val2)_ is successful |
| `...` | `...` | `...` |
The difference between this and the previous two groups of macros is that instead of
a predicate, `(ASSERT|EXPECT)_PRED_FORMAT*` take a _predicate-formatter_
(_pred\_formatn_), which is a function or functor with the signature:
`::testing::AssertionResult PredicateFormattern(const char* `_expr1_`, const char* `_expr2_`, ... const char* `_exprn_`, T1 `_val1_`, T2 `_val2_`, ... Tn `_valn_`);`
where _val1_, _val2_, ..., and _valn_ are the values of the predicate
arguments, and _expr1_, _expr2_, ..., and _exprn_ are the corresponding
expressions as they appear in the source code. The types `T1`, `T2`, ..., and
`Tn` can be either value types or reference types. For example, if an
argument has type `Foo`, you can declare it as either `Foo` or `const Foo&`,
whichever is appropriate.
A predicate-formatter returns a `::testing::AssertionResult` object to indicate
whether the assertion has succeeded or not. The only way to create such an
object is to call one of these factory functions:
As an example, let's improve the failure message in the previous example, which uses `EXPECT_PRED2()`:
```
// Returns the smallest prime common divisor of m and n,
// or 1 when m and n are mutually prime.
int SmallestPrimeCommonDivisor(int m, int n) { ... }
// A predicate-formatter for asserting that two integers are mutually prime.
::testing::AssertionResult AssertMutuallyPrime(const char* m_expr,
const char* n_expr,
int m,
int n) {
if (MutuallyPrime(m, n))
return ::testing::AssertionSuccess();
return ::testing::AssertionFailure()
<< m_expr << " and " << n_expr << " (" << m << " and " << n
<< ") are not mutually prime, " << "as they have a common divisor "
<< SmallestPrimeCommonDivisor(m, n);
}
```
With this predicate-formatter, we can use
```
EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);
```
to generate the message
<pre>
b and c (4 and 10) are not mutually prime, as they have a common divisor 2.<br>
</pre>
As you may have realized, many of the assertions we introduced earlier are
special cases of `(EXPECT|ASSERT)_PRED_FORMAT*`. In fact, most of them are
indeed defined using `(EXPECT|ASSERT)_PRED_FORMAT*`.
_Availability_: Linux, Windows, Mac.
## Floating-Point Comparison ##
Comparing floating-point numbers is tricky. Due to round-off errors, it is
very unlikely that two floating-points will match exactly. Therefore,
`ASSERT_EQ` 's naive comparison usually doesn't work. And since floating-points
can have a wide value range, no single fixed error bound works. It's better to
compare by a fixed relative error bound, except for values close to 0 due to
the loss of precision there.
In general, for floating-point comparison to make sense, the user needs to
carefully choose the error bound. If they don't want or care to, comparing in
terms of Units in the Last Place (ULPs) is a good default, and Google Test
provides assertions to do this. Full details about ULPs are quite long; if you
want to learn more, see
[this article on float comparison](http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm).
### Floating-Point Macros ###
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_FLOAT_EQ(`_expected, actual_`);` | `EXPECT_FLOAT_EQ(`_expected, actual_`);` | the two `float` values are almost equal |
| `ASSERT_DOUBLE_EQ(`_expected, actual_`);` | `EXPECT_DOUBLE_EQ(`_expected, actual_`);` | the two `double` values are almost equal |
By "almost equal", we mean the two values are within 4 ULP's from each
other.
The following assertions allow you to choose the acceptable error bound:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_NEAR(`_val1, val2, abs\_error_`);` | `EXPECT_NEAR`_(val1, val2, abs\_error_`);` | the difference between _val1_ and _val2_ doesn't exceed the given absolute error |
_Availability_: Linux, Windows, Mac.
### Floating-Point Predicate-Format Functions ###
Some floating-point operations are useful, but not that often used. In order
to avoid an explosion of new macros, we provide them as predicate-format
functions that can be used in predicate assertion macros (e.g.
`EXPECT_PRED_FORMAT2`, etc).
```
EXPECT_PRED_FORMAT2(::testing::FloatLE, val1, val2);
EXPECT_PRED_FORMAT2(::testing::DoubleLE, val1, val2);
```
Verifies that _val1_ is less than, or almost equal to, _val2_. You can
replace `EXPECT_PRED_FORMAT2` in the above table with `ASSERT_PRED_FORMAT2`.
_Availability_: Linux, Windows, Mac.
## Windows HRESULT assertions ##
These assertions test for `HRESULT` success or failure.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_HRESULT_SUCCEEDED(`_expression_`);` | `EXPECT_HRESULT_SUCCEEDED(`_expression_`);` | _expression_ is a success `HRESULT` |
| `ASSERT_HRESULT_FAILED(`_expression_`);` | `EXPECT_HRESULT_FAILED(`_expression_`);` | _expression_ is a failure `HRESULT` |
The generated output contains the human-readable error message
associated with the `HRESULT` code returned by _expression_.
You might use them like this:
```
CComPtr shell;
ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application"));
CComVariant empty;
ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty));
```
_Availability_: Windows.
## Type Assertions ##
You can call the function
```
::testing::StaticAssertTypeEq<T1, T2>();
```
to assert that types `T1` and `T2` are the same. The function does
nothing if the assertion is satisfied. If the types are different,
the function call will fail to compile, and the compiler error message
will likely (depending on the compiler) show you the actual values of
`T1` and `T2`. This is mainly useful inside template code.
_Caveat:_ When used inside a member function of a class template or a
function template, `StaticAssertTypeEq<T1, T2>()` is effective _only if_
the function is instantiated. For example, given:
```
template <typename T> class Foo {
public:
void Bar() { ::testing::StaticAssertTypeEq<int, T>(); }
};
```
the code:
```
void Test1() { Foo<bool> foo; }
```
will _not_ generate a compiler error, as `Foo<bool>::Bar()` is never
actually instantiated. Instead, you need:
```
void Test2() { Foo<bool> foo; foo.Bar(); }
```
to cause a compiler error.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
## Assertion Placement ##
You can use assertions in any C++ function. In particular, it doesn't
have to be a method of the test fixture class. The one constraint is
that assertions that generate a fatal failure (`FAIL*` and `ASSERT_*`)
can only be used in void-returning functions. This is a consequence of
Google Test not using exceptions. By placing it in a non-void function
you'll get a confusing compile error like
`"error: void value not ignored as it ought to be"`.
If you need to use assertions in a function that returns non-void, one option
is to make the function return the value in an out parameter instead. For
example, you can rewrite `T2 Foo(T1 x)` to `void Foo(T1 x, T2* result)`. You
need to make sure that `*result` contains some sensible value even when the
function returns prematurely. As the function now returns `void`, you can use
any assertion inside of it.
If changing the function's type is not an option, you should just use
assertions that generate non-fatal failures, such as `ADD_FAILURE*` and
`EXPECT_*`.
_Note_: Constructors and destructors are not considered void-returning
functions, according to the C++ language specification, and so you may not use
fatal assertions in them. You'll get a compilation error if you try. A simple
workaround is to transfer the entire body of the constructor or destructor to a
private void-returning method. However, you should be aware that a fatal
assertion failure in a constructor does not terminate the current test, as your
intuition might suggest; it merely returns from the constructor early, possibly
leaving your object in a partially-constructed state. Likewise, a fatal
assertion failure in a destructor may leave your object in a
partially-destructed state. Use assertions carefully in these situations!
# Teaching Google Test How to Print Your Values #
When a test assertion such as `EXPECT_EQ` fails, Google Test prints the
argument values to help you debug. It does this using a
user-extensible value printer.
This printer knows how to print built-in C++ types, native arrays, STL
containers, and any type that supports the `<<` operator. For other
types, it prints the raw bytes in the value and hopes that you the
user can figure it out.
As mentioned earlier, the printer is _extensible_. That means
you can teach it to do a better job at printing your particular type
than to dump the bytes. To do that, define `<<` for your type:
```
#include <iostream>
namespace foo {
class Bar { ... }; // We want Google Test to be able to print instances of this.
// It's important that the << operator is defined in the SAME
// namespace that defines Bar. C++'s look-up rules rely on that.
::std::ostream& operator<<(::std::ostream& os, const Bar& bar) {
return os << bar.DebugString(); // whatever needed to print bar to os
}
} // namespace foo
```
Sometimes, this might not be an option: your team may consider it bad
style to have a `<<` operator for `Bar`, or `Bar` may already have a
`<<` operator that doesn't do what you want (and you cannot change
it). If so, you can instead define a `PrintTo()` function like this:
```
#include <iostream>
namespace foo {
class Bar { ... };
// It's important that PrintTo() is defined in the SAME
// namespace that defines Bar. C++'s look-up rules rely on that.
void PrintTo(const Bar& bar, ::std::ostream* os) {
*os << bar.DebugString(); // whatever needed to print bar to os
}
} // namespace foo
```
If you have defined both `<<` and `PrintTo()`, the latter will be used
when Google Test is concerned. This allows you to customize how the value
appears in Google Test's output without affecting code that relies on the
behavior of its `<<` operator.
If you want to print a value `x` using Google Test's value printer
yourself, just call `::testing::PrintToString(`_x_`)`, which
returns an `std::string`:
```
vector<pair<Bar, int> > bar_ints = GetBarIntVector();
EXPECT_TRUE(IsCorrectBarIntVector(bar_ints))
<< "bar_ints = " << ::testing::PrintToString(bar_ints);
```
# Death Tests #
In many applications, there are assertions that can cause application failure
if a condition is not met. These sanity checks, which ensure that the program
is in a known good state, are there to fail at the earliest possible time after
some program state is corrupted. If the assertion checks the wrong condition,
then the program may proceed in an erroneous state, which could lead to memory
corruption, security holes, or worse. Hence it is vitally important to test
that such assertion statements work as expected.
Since these precondition checks cause the processes to die, we call such tests
_death tests_. More generally, any test that checks that a program terminates
(except by throwing an exception) in an expected fashion is also a death test.
Note that if a piece of code throws an exception, we don't consider it "death"
for the purpose of death tests, as the caller of the code could catch the exception
and avoid the crash. If you want to verify exceptions thrown by your code,
see [Exception Assertions](#exception-assertions).
If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see [Catching Failures](#catching-failures).
## How to Write a Death Test ##
Google Test has the following macros to support death tests:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_DEATH(`_statement, regex_`); | `EXPECT_DEATH(`_statement, regex_`); | _statement_ crashes with the given error |
| `ASSERT_DEATH_IF_SUPPORTED(`_statement, regex_`); | `EXPECT_DEATH_IF_SUPPORTED(`_statement, regex_`); | if death tests are supported, verifies that _statement_ crashes with the given error; otherwise verifies nothing |
| `ASSERT_EXIT(`_statement, predicate, regex_`); | `EXPECT_EXIT(`_statement, predicate, regex_`); |_statement_ exits with the given error and its exit code matches _predicate_ |
where _statement_ is a statement that is expected to cause the process to
die, _predicate_ is a function or function object that evaluates an integer
exit status, and _regex_ is a regular expression that the stderr output of
_statement_ is expected to match. Note that _statement_ can be _any valid
statement_ (including _compound statement_) and doesn't have to be an
expression.
As usual, the `ASSERT` variants abort the current test function, while the
`EXPECT` variants do not.
**Note:** We use the word "crash" here to mean that the process
terminates with a _non-zero_ exit status code. There are two
possibilities: either the process has called `exit()` or `_exit()`
with a non-zero value, or it may be killed by a signal.
This means that if _statement_ terminates the process with a 0 exit
code, it is _not_ considered a crash by `EXPECT_DEATH`. Use
`EXPECT_EXIT` instead if this is the case, or if you want to restrict
the exit code more precisely.
A predicate here must accept an `int` and return a `bool`. The death test
succeeds only if the predicate returns `true`. Google Test defines a few
predicates that handle the most common cases:
```
::testing::ExitedWithCode(exit_code)
```
This expression is `true` if the program exited normally with the given exit
code.
```
::testing::KilledBySignal(signal_number) // Not available on Windows.
```
This expression is `true` if the program was killed by the given signal.
The `*_DEATH` macros are convenient wrappers for `*_EXIT` that use a predicate
that verifies the process' exit code is non-zero.
Note that a death test only cares about three things:
1. does _statement_ abort or exit the process?
1. (in the case of `ASSERT_EXIT` and `EXPECT_EXIT`) does the exit status satisfy _predicate_? Or (in the case of `ASSERT_DEATH` and `EXPECT_DEATH`) is the exit status non-zero? And
1. does the stderr output match _regex_?
In particular, if _statement_ generates an `ASSERT_*` or `EXPECT_*` failure, it will **not** cause the death test to fail, as Google Test assertions don't abort the process.
To write a death test, simply use one of the above macros inside your test
function. For example,
```
TEST(My*DeathTest*, Foo) {
// This death test uses a compound statement.
ASSERT_DEATH({ int n = 5; Foo(&n); }, "Error on line .* of Foo()");
}
TEST(MyDeathTest, NormalExit) {
EXPECT_EXIT(NormalExit(), ::testing::ExitedWithCode(0), "Success");
}
TEST(MyDeathTest, KillMyself) {
EXPECT_EXIT(KillMyself(), ::testing::KilledBySignal(SIGKILL), "Sending myself unblockable signal");
}
```
verifies that:
* calling `Foo(5)` causes the process to die with the given error message,
* calling `NormalExit()` causes the process to print `"Success"` to stderr and exit with exit code 0, and
* calling `KillMyself()` kills the process with signal `SIGKILL`.
The test function body may contain other assertions and statements as well, if
necessary.
_Important:_ We strongly recommend you to follow the convention of naming your
test case (not test) `*DeathTest` when it contains a death test, as
demonstrated in the above example. The `Death Tests And Threads` section below
explains why.
If a test fixture class is shared by normal tests and death tests, you
can use typedef to introduce an alias for the fixture class and avoid
duplicating its code:
```
class FooTest : public ::testing::Test { ... };
typedef FooTest FooDeathTest;
TEST_F(FooTest, DoesThis) {
// normal test
}
TEST_F(FooDeathTest, DoesThat) {
// death test
}
```
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Cygwin, and Mac (the latter three are supported since v1.3.0). `(ASSERT|EXPECT)_DEATH_IF_SUPPORTED` are new in v1.4.0.
## Regular Expression Syntax ##
On POSIX systems (e.g. Linux, Cygwin, and Mac), Google Test uses the
[POSIX extended regular expression](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
syntax in death tests. To learn about this syntax, you may want to read this [Wikipedia entry](http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions).
On Windows, Google Test uses its own simple regular expression
implementation. It lacks many features you can find in POSIX extended
regular expressions. For example, we don't support union (`"x|y"`),
grouping (`"(xy)"`), brackets (`"[xy]"`), and repetition count
(`"x{5,7}"`), among others. Below is what we do support (`A` denotes a
literal character, period (`.`), or a single `\\` escape sequence; `x`
and `y` denote regular expressions.):
| `c` | matches any literal character `c` |
|:----|:----------------------------------|
| `\\d` | matches any decimal digit |
| `\\D` | matches any character that's not a decimal digit |
| `\\f` | matches `\f` |
| `\\n` | matches `\n` |
| `\\r` | matches `\r` |
| `\\s` | matches any ASCII whitespace, including `\n` |
| `\\S` | matches any character that's not a whitespace |
| `\\t` | matches `\t` |
| `\\v` | matches `\v` |
| `\\w` | matches any letter, `_`, or decimal digit |
| `\\W` | matches any character that `\\w` doesn't match |
| `\\c` | matches any literal character `c`, which must be a punctuation |
| `.` | matches any single character except `\n` |
| `A?` | matches 0 or 1 occurrences of `A` |
| `A*` | matches 0 or many occurrences of `A` |
| `A+` | matches 1 or many occurrences of `A` |
| `^` | matches the beginning of a string (not that of each line) |
| `$` | matches the end of a string (not that of each line) |
| `xy` | matches `x` followed by `y` |
To help you determine which capability is available on your system,
Google Test defines macro `GTEST_USES_POSIX_RE=1` when it uses POSIX
extended regular expressions, or `GTEST_USES_SIMPLE_RE=1` when it uses
the simple version. If you want your death tests to work in both
cases, you can either `#if` on these macros or use the more limited
syntax only.
## How It Works ##
Under the hood, `ASSERT_EXIT()` spawns a new process and executes the
death test statement in that process. The details of how precisely
that happens depend on the platform and the variable
`::testing::GTEST_FLAG(death_test_style)` (which is initialized from the
command-line flag `--gtest_death_test_style`).
* On POSIX systems, `fork()` (or `clone()` on Linux) is used to spawn the child, after which:
* If the variable's value is `"fast"`, the death test statement is immediately executed.
* If the variable's value is `"threadsafe"`, the child process re-executes the unit test binary just as it was originally invoked, but with some extra flags to cause just the single death test under consideration to be run.
* On Windows, the child is spawned using the `CreateProcess()` API, and re-executes the binary to cause just the single death test under consideration to be run - much like the `threadsafe` mode on POSIX.
Other values for the variable are illegal and will cause the death test to
fail. Currently, the flag's default value is `"fast"`. However, we reserve the
right to change it in the future. Therefore, your tests should not depend on
this.
In either case, the parent process waits for the child process to complete, and checks that
1. the child's exit status satisfies the predicate, and
1. the child's stderr matches the regular expression.
If the death test statement runs to completion without dying, the child
process will nonetheless terminate, and the assertion fails.
## Death Tests And Threads ##
The reason for the two death test styles has to do with thread safety. Due to
well-known problems with forking in the presence of threads, death tests should
be run in a single-threaded context. Sometimes, however, it isn't feasible to
arrange that kind of environment. For example, statically-initialized modules
may start threads before main is ever reached. Once threads have been created,
it may be difficult or impossible to clean them up.
Google Test has three features intended to raise awareness of threading issues.
1. A warning is emitted if multiple threads are running when a death test is encountered.
1. Test cases with a name ending in "DeathTest" are run before all other tests.
1. It uses `clone()` instead of `fork()` to spawn the child process on Linux (`clone()` is not available on Cygwin and Mac), as `fork()` is more likely to cause the child to hang when the parent process has multiple threads.
It's perfectly fine to create threads inside a death test statement; they are
executed in a separate process and cannot affect the parent.
## Death Test Styles ##
The "threadsafe" death test style was introduced in order to help mitigate the
risks of testing in a possibly multithreaded environment. It trades increased
test execution time (potentially dramatically so) for improved thread safety.
We suggest using the faster, default "fast" style unless your test has specific
problems with it.
You can choose a particular style of death tests by setting the flag
programmatically:
```
::testing::FLAGS_gtest_death_test_style = "threadsafe";
```
You can do this in `main()` to set the style for all death tests in the
binary, or in individual tests. Recall that flags are saved before running each
test and restored afterwards, so you need not do that yourself. For example:
```
TEST(MyDeathTest, TestOne) {
::testing::FLAGS_gtest_death_test_style = "threadsafe";
// This test is run in the "threadsafe" style:
ASSERT_DEATH(ThisShouldDie(), "");
}
TEST(MyDeathTest, TestTwo) {
// This test is run in the "fast" style:
ASSERT_DEATH(ThisShouldDie(), "");
}
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
::testing::FLAGS_gtest_death_test_style = "fast";
return RUN_ALL_TESTS();
}
```
## Caveats ##
The _statement_ argument of `ASSERT_EXIT()` can be any valid C++ statement.
If it leaves the current function via a `return` statement or by throwing an exception,
the death test is considered to have failed. Some Google Test macros may return
from the current function (e.g. `ASSERT_TRUE()`), so be sure to avoid them in _statement_.
Since _statement_ runs in the child process, any in-memory side effect (e.g.
modifying a variable, releasing memory, etc) it causes will _not_ be observable
in the parent process. In particular, if you release memory in a death test,
your program will fail the heap check as the parent process will never see the
memory reclaimed. To solve this problem, you can
1. try not to free memory in a death test;
1. free the memory again in the parent process; or
1. do not use the heap checker in your program.
Due to an implementation detail, you cannot place multiple death test
assertions on the same line; otherwise, compilation will fail with an unobvious
error message.
Despite the improved thread safety afforded by the "threadsafe" style of death
test, thread problems such as deadlock are still possible in the presence of
handlers registered with `pthread_atfork(3)`.
# Using Assertions in Sub-routines #
## Adding Traces to Assertions ##
If a test sub-routine is called from several places, when an assertion
inside it fails, it can be hard to tell which invocation of the
sub-routine the failure is from. You can alleviate this problem using
extra logging or custom failure messages, but that usually clutters up
your tests. A better solution is to use the `SCOPED_TRACE` macro:
| `SCOPED_TRACE(`_message_`);` |
|:-----------------------------|
where _message_ can be anything streamable to `std::ostream`. This
macro will cause the current file name, line number, and the given
message to be added in every failure message. The effect will be
undone when the control leaves the current lexical scope.
For example,
```
10: void Sub1(int n) {
11: EXPECT_EQ(1, Bar(n));
12: EXPECT_EQ(2, Bar(n + 1));
13: }
14:
15: TEST(FooTest, Bar) {
16: {
17: SCOPED_TRACE("A"); // This trace point will be included in
18: // every failure in this scope.
19: Sub1(1);
20: }
21: // Now it won't.
22: Sub1(9);
23: }
```
could result in messages like these:
```
path/to/foo_test.cc:11: Failure
Value of: Bar(n)
Expected: 1
Actual: 2
Trace:
path/to/foo_test.cc:17: A
path/to/foo_test.cc:12: Failure
Value of: Bar(n + 1)
Expected: 2
Actual: 3
```
Without the trace, it would've been difficult to know which invocation
of `Sub1()` the two failures come from respectively. (You could add an
extra message to each assertion in `Sub1()` to indicate the value of
`n`, but that's tedious.)
Some tips on using `SCOPED_TRACE`:
1. With a suitable message, it's often enough to use `SCOPED_TRACE` at the beginning of a sub-routine, instead of at each call site.
1. When calling sub-routines inside a loop, make the loop iterator part of the message in `SCOPED_TRACE` such that you can know which iteration the failure is from.
1. Sometimes the line number of the trace point is enough for identifying the particular invocation of a sub-routine. In this case, you don't have to choose a unique message for `SCOPED_TRACE`. You can simply use `""`.
1. You can use `SCOPED_TRACE` in an inner scope when there is one in the outer scope. In this case, all active trace points will be included in the failure messages, in reverse order they are encountered.
1. The trace dump is clickable in Emacs' compilation buffer - hit return on a line number and you'll be taken to that line in the source file!
_Availability:_ Linux, Windows, Mac.
## Propagating Fatal Failures ##
A common pitfall when using `ASSERT_*` and `FAIL*` is not understanding that
when they fail they only abort the _current function_, not the entire test. For
example, the following test will segfault:
```
void Subroutine() {
// Generates a fatal failure and aborts the current function.
ASSERT_EQ(1, 2);
// The following won't be executed.
...
}
TEST(FooTest, Bar) {
Subroutine();
// The intended behavior is for the fatal failure
// in Subroutine() to abort the entire test.
// The actual behavior: the function goes on after Subroutine() returns.
int* p = NULL;
*p = 3; // Segfault!
}
```
Since we don't use exceptions, it is technically impossible to
implement the intended behavior here. To alleviate this, Google Test
provides two solutions. You could use either the
`(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the
`HasFatalFailure()` function. They are described in the following two
subsections.
### Asserting on Subroutines ###
As shown above, if your test calls a subroutine that has an `ASSERT_*`
failure in it, the test will continue after the subroutine
returns. This may not be what you want.
Often people want fatal failures to propagate like exceptions. For
that Google Test offers the following macros:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_NO_FATAL_FAILURE(`_statement_`);` | `EXPECT_NO_FATAL_FAILURE(`_statement_`);` | _statement_ doesn't generate any new fatal failures in the current thread. |
Only failures in the thread that executes the assertion are checked to
determine the result of this type of assertions. If _statement_
creates new threads, failures in these threads are ignored.
Examples:
```
ASSERT_NO_FATAL_FAILURE(Foo());
int i;
EXPECT_NO_FATAL_FAILURE({
i = Bar();
});
```
_Availability:_ Linux, Windows, Mac. Assertions from multiple threads
are currently not supported.
### Checking for Failures in the Current Test ###
`HasFatalFailure()` in the `::testing::Test` class returns `true` if an
assertion in the current test has suffered a fatal failure. This
allows functions to catch fatal failures in a sub-routine and return
early.
```
class Test {
public:
...
static bool HasFatalFailure();
};
```
The typical usage, which basically simulates the behavior of a thrown
exception, is:
```
TEST(FooTest, Bar) {
Subroutine();
// Aborts if Subroutine() had a fatal failure.
if (HasFatalFailure())
return;
// The following won't be executed.
...
}
```
If `HasFatalFailure()` is used outside of `TEST()` , `TEST_F()` , or a test
fixture, you must add the `::testing::Test::` prefix, as in:
```
if (::testing::Test::HasFatalFailure())
return;
```
Similarly, `HasNonfatalFailure()` returns `true` if the current test
has at least one non-fatal failure, and `HasFailure()` returns `true`
if the current test has at least one failure of either kind.
_Availability:_ Linux, Windows, Mac. `HasNonfatalFailure()` and
`HasFailure()` are available since version 1.4.0.
# Logging Additional Information #
In your test code, you can call `RecordProperty("key", value)` to log
additional information, where `value` can be either a C string or a 32-bit
integer. The _last_ value recorded for a key will be emitted to the XML output
if you specify one. For example, the test
```
TEST_F(WidgetUsageTest, MinAndMaxWidgets) {
RecordProperty("MaximumWidgets", ComputeMaxUsage());
RecordProperty("MinimumWidgets", ComputeMinUsage());
}
```
will output XML like this:
```
...
<testcase name="MinAndMaxWidgets" status="run" time="6" classname="WidgetUsageTest"
MaximumWidgets="12"
MinimumWidgets="9" />
...
```
_Note_:
* `RecordProperty()` is a static member of the `Test` class. Therefore it needs to be prefixed with `::testing::Test::` if used outside of the `TEST` body and the test fixture class.
* `key` must be a valid XML attribute name, and cannot conflict with the ones already used by Google Test (`name`, `status`, `time`, and `classname`).
_Availability_: Linux, Windows, Mac.
# Sharing Resources Between Tests in the Same Test Case #
Google Test creates a new test fixture object for each test in order to make
tests independent and easier to debug. However, sometimes tests use resources
that are expensive to set up, making the one-copy-per-test model prohibitively
expensive.
If the tests don't change the resource, there's no harm in them sharing a
single resource copy. So, in addition to per-test set-up/tear-down, Google Test
also supports per-test-case set-up/tear-down. To use it:
1. In your test fixture class (say `FooTest` ), define as `static` some member variables to hold the shared resources.
1. In the same test fixture class, define a `static void SetUpTestCase()` function (remember not to spell it as **`SetupTestCase`** with a small `u`!) to set up the shared resources and a `static void TearDownTestCase()` function to tear them down.
That's it! Google Test automatically calls `SetUpTestCase()` before running the
_first test_ in the `FooTest` test case (i.e. before creating the first
`FooTest` object), and calls `TearDownTestCase()` after running the _last test_
in it (i.e. after deleting the last `FooTest` object). In between, the tests
can use the shared resources.
Remember that the test order is undefined, so your code can't depend on a test
preceding or following another. Also, the tests must either not modify the
state of any shared resource, or, if they do modify the state, they must
restore the state to its original value before passing control to the next
test.
Here's an example of per-test-case set-up and tear-down:
```
class FooTest : public ::testing::Test {
protected:
// Per-test-case set-up.
// Called before the first test in this test case.
// Can be omitted if not needed.
static void SetUpTestCase() {
shared_resource_ = new ...;
}
// Per-test-case tear-down.
// Called after the last test in this test case.
// Can be omitted if not needed.
static void TearDownTestCase() {
delete shared_resource_;
shared_resource_ = NULL;
}
// You can define per-test set-up and tear-down logic as usual.
virtual void SetUp() { ... }
virtual void TearDown() { ... }
// Some expensive resource shared by all tests.
static T* shared_resource_;
};
T* FooTest::shared_resource_ = NULL;
TEST_F(FooTest, Test1) {
... you can refer to shared_resource here ...
}
TEST_F(FooTest, Test2) {
... you can refer to shared_resource here ...
}
```
_Availability:_ Linux, Windows, Mac.
# Global Set-Up and Tear-Down #
Just as you can do set-up and tear-down at the test level and the test case
level, you can also do it at the test program level. Here's how.
First, you subclass the `::testing::Environment` class to define a test
environment, which knows how to set-up and tear-down:
```
class Environment {
public:
virtual ~Environment() {}
// Override this to define how to set up the environment.
virtual void SetUp() {}
// Override this to define how to tear down the environment.
virtual void TearDown() {}
};
```
Then, you register an instance of your environment class with Google Test by
calling the `::testing::AddGlobalTestEnvironment()` function:
```
Environment* AddGlobalTestEnvironment(Environment* env);
```
Now, when `RUN_ALL_TESTS()` is called, it first calls the `SetUp()` method of
the environment object, then runs the tests if there was no fatal failures, and
finally calls `TearDown()` of the environment object.
It's OK to register multiple environment objects. In this case, their `SetUp()`
will be called in the order they are registered, and their `TearDown()` will be
called in the reverse order.
Note that Google Test takes ownership of the registered environment objects.
Therefore **do not delete them** by yourself.
You should call `AddGlobalTestEnvironment()` before `RUN_ALL_TESTS()` is
called, probably in `main()`. If you use `gtest_main`, you need to call
this before `main()` starts for it to take effect. One way to do this is to
define a global variable like this:
```
::testing::Environment* const foo_env = ::testing::AddGlobalTestEnvironment(new FooEnvironment);
```
However, we strongly recommend you to write your own `main()` and call
`AddGlobalTestEnvironment()` there, as relying on initialization of global
variables makes the code harder to read and may cause problems when you
register multiple environments from different translation units and the
environments have dependencies among them (remember that the compiler doesn't
guarantee the order in which global variables from different translation units
are initialized).
_Availability:_ Linux, Windows, Mac.
# Value Parameterized Tests #
_Value-parameterized tests_ allow you to test your code with different
parameters without writing multiple copies of the same test.
Suppose you write a test for your code and then realize that your code is affected by a presence of a Boolean command line flag.
```
TEST(MyCodeTest, TestFoo) {
// A code to test foo().
}
```
Usually people factor their test code into a function with a Boolean parameter in such situations. The function sets the flag, then executes the testing code.
```
void TestFooHelper(bool flag_value) {
flag = flag_value;
// A code to test foo().
}
TEST(MyCodeTest, TestFooo) {
TestFooHelper(false);
TestFooHelper(true);
}
```
But this setup has serious drawbacks. First, when a test assertion fails in your tests, it becomes unclear what value of the parameter caused it to fail. You can stream a clarifying message into your `EXPECT`/`ASSERT` statements, but it you'll have to do it with all of them. Second, you have to add one such helper function per test. What if you have ten tests? Twenty? A hundred?
Value-parameterized tests will let you write your test only once and then easily instantiate and run it with an arbitrary number of parameter values.
Here are some other situations when value-parameterized tests come handy:
* You want to test different implementations of an OO interface.
* You want to test your code over various inputs (a.k.a. data-driven testing). This feature is easy to abuse, so please exercise your good sense when doing it!
## How to Write Value-Parameterized Tests ##
To write value-parameterized tests, first you should define a fixture
class. It must be derived from both `::testing::Test` and
`::testing::WithParamInterface<T>` (the latter is a pure interface),
where `T` is the type of your parameter values. For convenience, you
can just derive the fixture class from `::testing::TestWithParam<T>`,
which itself is derived from both `::testing::Test` and
`::testing::WithParamInterface<T>`. `T` can be any copyable type. If
it's a raw pointer, you are responsible for managing the lifespan of
the pointed values.
```
class FooTest : public ::testing::TestWithParam<const char*> {
// You can implement all the usual fixture class members here.
// To access the test parameter, call GetParam() from class
// TestWithParam<T>.
};
// Or, when you want to add parameters to a pre-existing fixture class:
class BaseTest : public ::testing::Test {
...
};
class BarTest : public BaseTest,
public ::testing::WithParamInterface<const char*> {
...
};
```
Then, use the `TEST_P` macro to define as many test patterns using
this fixture as you want. The `_P` suffix is for "parameterized" or
"pattern", whichever you prefer to think.
```
TEST_P(FooTest, DoesBlah) {
// Inside a test, access the test parameter with the GetParam() method
// of the TestWithParam<T> class:
EXPECT_TRUE(foo.Blah(GetParam()));
...
}
TEST_P(FooTest, HasBlahBlah) {
...
}
```
Finally, you can use `INSTANTIATE_TEST_CASE_P` to instantiate the test
case with any set of parameters you want. Google Test defines a number of
functions for generating test parameters. They return what we call
(surprise!) _parameter generators_. Here is a summary of them,
which are all in the `testing` namespace:
| `Range(begin, end[, step])` | Yields values `{begin, begin+step, begin+step+step, ...}`. The values do not include `end`. `step` defaults to 1. |
|:----------------------------|:------------------------------------------------------------------------------------------------------------------|
| `Values(v1, v2, ..., vN)` | Yields values `{v1, v2, ..., vN}`. |
| `ValuesIn(container)` and `ValuesIn(begin, end)` | Yields values from a C-style array, an STL-style container, or an iterator range `[begin, end)`. `container`, `begin`, and `end` can be expressions whose values are determined at run time. |
| `Bool()` | Yields sequence `{false, true}`. |
| `Combine(g1, g2, ..., gN)` | Yields all combinations (the Cartesian product for the math savvy) of the values generated by the `N` generators. This is only available if your system provides the `<tr1/tuple>` header. If you are sure your system does, and Google Test disagrees, you can override it by defining `GTEST_HAS_TR1_TUPLE=1`. See comments in [include/gtest/internal/gtest-port.h](../include/gtest/internal/gtest-port.h) for more information. |
For more details, see the comments at the definitions of these functions in the [source code](../include/gtest/gtest-param-test.h).
The following statement will instantiate tests from the `FooTest` test case
each with parameter values `"meeny"`, `"miny"`, and `"moe"`.
```
INSTANTIATE_TEST_CASE_P(InstantiationName,
FooTest,
::testing::Values("meeny", "miny", "moe"));
```
To distinguish different instances of the pattern (yes, you can
instantiate it more than once), the first argument to
`INSTANTIATE_TEST_CASE_P` is a prefix that will be added to the actual
test case name. Remember to pick unique prefixes for different
instantiations. The tests from the instantiation above will have these
names:
* `InstantiationName/FooTest.DoesBlah/0` for `"meeny"`
* `InstantiationName/FooTest.DoesBlah/1` for `"miny"`
* `InstantiationName/FooTest.DoesBlah/2` for `"moe"`
* `InstantiationName/FooTest.HasBlahBlah/0` for `"meeny"`
* `InstantiationName/FooTest.HasBlahBlah/1` for `"miny"`
* `InstantiationName/FooTest.HasBlahBlah/2` for `"moe"`
You can use these names in [--gtest\-filter](#running-a-subset-of-the-tests).
This statement will instantiate all tests from `FooTest` again, each
with parameter values `"cat"` and `"dog"`:
```
const char* pets[] = {"cat", "dog"};
INSTANTIATE_TEST_CASE_P(AnotherInstantiationName, FooTest,
::testing::ValuesIn(pets));
```
The tests from the instantiation above will have these names:
* `AnotherInstantiationName/FooTest.DoesBlah/0` for `"cat"`
* `AnotherInstantiationName/FooTest.DoesBlah/1` for `"dog"`
* `AnotherInstantiationName/FooTest.HasBlahBlah/0` for `"cat"`
* `AnotherInstantiationName/FooTest.HasBlahBlah/1` for `"dog"`
Please note that `INSTANTIATE_TEST_CASE_P` will instantiate _all_
tests in the given test case, whether their definitions come before or
_after_ the `INSTANTIATE_TEST_CASE_P` statement.
You can see
[these](../samples/sample7_unittest.cc)
[files](../samples/sample8_unittest.cc) for more examples.
_Availability_: Linux, Windows (requires MSVC 8.0 or above), Mac; since version 1.2.0.
## Creating Value-Parameterized Abstract Tests ##
In the above, we define and instantiate `FooTest` in the same source
file. Sometimes you may want to define value-parameterized tests in a
library and let other people instantiate them later. This pattern is
known as <i>abstract tests</i>. As an example of its application, when you
are designing an interface you can write a standard suite of abstract
tests (perhaps using a factory function as the test parameter) that
all implementations of the interface are expected to pass. When
someone implements the interface, he can instantiate your suite to get
all the interface-conformance tests for free.
To define abstract tests, you should organize your code like this:
1. Put the definition of the parameterized test fixture class (e.g. `FooTest`) in a header file, say `foo_param_test.h`. Think of this as _declaring_ your abstract tests.
1. Put the `TEST_P` definitions in `foo_param_test.cc`, which includes `foo_param_test.h`. Think of this as _implementing_ your abstract tests.
Once they are defined, you can instantiate them by including
`foo_param_test.h`, invoking `INSTANTIATE_TEST_CASE_P()`, and linking
with `foo_param_test.cc`. You can instantiate the same abstract test
case multiple times, possibly in different source files.
# Typed Tests #
Suppose you have multiple implementations of the same interface and
want to make sure that all of them satisfy some common requirements.
Or, you may have defined several types that are supposed to conform to
the same "concept" and you want to verify it. In both cases, you want
the same test logic repeated for different types.
While you can write one `TEST` or `TEST_F` for each type you want to
test (and you may even factor the test logic into a function template
that you invoke from the `TEST`), it's tedious and doesn't scale:
if you want _m_ tests over _n_ types, you'll end up writing _m\*n_
`TEST`s.
_Typed tests_ allow you to repeat the same test logic over a list of
types. You only need to write the test logic once, although you must
know the type list when writing typed tests. Here's how you do it:
First, define a fixture class template. It should be parameterized
by a type. Remember to derive it from `::testing::Test`:
```
template <typename T>
class FooTest : public ::testing::Test {
public:
...
typedef std::list<T> List;
static T shared_;
T value_;
};
```
Next, associate a list of types with the test case, which will be
repeated for each type in the list:
```
typedef ::testing::Types<char, int, unsigned int> MyTypes;
TYPED_TEST_CASE(FooTest, MyTypes);
```
The `typedef` is necessary for the `TYPED_TEST_CASE` macro to parse
correctly. Otherwise the compiler will think that each comma in the
type list introduces a new macro argument.
Then, use `TYPED_TEST()` instead of `TEST_F()` to define a typed test
for this test case. You can repeat this as many times as you want:
```
TYPED_TEST(FooTest, DoesBlah) {
// Inside a test, refer to the special name TypeParam to get the type
// parameter. Since we are inside a derived class template, C++ requires
// us to visit the members of FooTest via 'this'.
TypeParam n = this->value_;
// To visit static members of the fixture, add the 'TestFixture::'
// prefix.
n += TestFixture::shared_;
// To refer to typedefs in the fixture, add the 'typename TestFixture::'
// prefix. The 'typename' is required to satisfy the compiler.
typename TestFixture::List values;
values.push_back(n);
...
}
TYPED_TEST(FooTest, HasPropertyA) { ... }
```
You can see `samples/sample6_unittest.cc` for a complete example.
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Mac;
since version 1.1.0.
# Type-Parameterized Tests #
_Type-parameterized tests_ are like typed tests, except that they
don't require you to know the list of types ahead of time. Instead,
you can define the test logic first and instantiate it with different
type lists later. You can even instantiate it more than once in the
same program.
If you are designing an interface or concept, you can define a suite
of type-parameterized tests to verify properties that any valid
implementation of the interface/concept should have. Then, the author
of each implementation can just instantiate the test suite with his
type to verify that it conforms to the requirements, without having to
write similar tests repeatedly. Here's an example:
First, define a fixture class template, as we did with typed tests:
```
template <typename T>
class FooTest : public ::testing::Test {
...
};
```
Next, declare that you will define a type-parameterized test case:
```
TYPED_TEST_CASE_P(FooTest);
```
The `_P` suffix is for "parameterized" or "pattern", whichever you
prefer to think.
Then, use `TYPED_TEST_P()` to define a type-parameterized test. You
can repeat this as many times as you want:
```
TYPED_TEST_P(FooTest, DoesBlah) {
// Inside a test, refer to TypeParam to get the type parameter.
TypeParam n = 0;
...
}
TYPED_TEST_P(FooTest, HasPropertyA) { ... }
```
Now the tricky part: you need to register all test patterns using the
`REGISTER_TYPED_TEST_CASE_P` macro before you can instantiate them.
The first argument of the macro is the test case name; the rest are
the names of the tests in this test case:
```
REGISTER_TYPED_TEST_CASE_P(FooTest,
DoesBlah, HasPropertyA);
```
Finally, you are free to instantiate the pattern with the types you
want. If you put the above code in a header file, you can `#include`
it in multiple C++ source files and instantiate it multiple times.
```
typedef ::testing::Types<char, int, unsigned int> MyTypes;
INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, MyTypes);
```
To distinguish different instances of the pattern, the first argument
to the `INSTANTIATE_TYPED_TEST_CASE_P` macro is a prefix that will be
added to the actual test case name. Remember to pick unique prefixes
for different instances.
In the special case where the type list contains only one type, you
can write that type directly without `::testing::Types<...>`, like this:
```
INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, int);
```
You can see `samples/sample6_unittest.cc` for a complete example.
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Mac;
since version 1.1.0.
# Testing Private Code #
If you change your software's internal implementation, your tests should not
break as long as the change is not observable by users. Therefore, per the
_black-box testing principle_, most of the time you should test your code
through its public interfaces.
If you still find yourself needing to test internal implementation code,
consider if there's a better design that wouldn't require you to do so. If you
absolutely have to test non-public interface code though, you can. There are
two cases to consider:
* Static functions (_not_ the same as static member functions!) or unnamed namespaces, and
* Private or protected class members
## Static Functions ##
Both static functions and definitions/declarations in an unnamed namespace are
only visible within the same translation unit. To test them, you can `#include`
the entire `.cc` file being tested in your `*_test.cc` file. (`#include`ing `.cc`
files is not a good way to reuse code - you should not do this in production
code!)
However, a better approach is to move the private code into the
`foo::internal` namespace, where `foo` is the namespace your project normally
uses, and put the private declarations in a `*-internal.h` file. Your
production `.cc` files and your tests are allowed to include this internal
header, but your clients are not. This way, you can fully test your internal
implementation without leaking it to your clients.
## Private Class Members ##
Private class members are only accessible from within the class or by friends.
To access a class' private members, you can declare your test fixture as a
friend to the class and define accessors in your fixture. Tests using the
fixture can then access the private members of your production class via the
accessors in the fixture. Note that even though your fixture is a friend to
your production class, your tests are not automatically friends to it, as they
are technically defined in sub-classes of the fixture.
Another way to test private members is to refactor them into an implementation
class, which is then declared in a `*-internal.h` file. Your clients aren't
allowed to include this header but your tests can. Such is called the Pimpl
(Private Implementation) idiom.
Or, you can declare an individual test as a friend of your class by adding this
line in the class body:
```
FRIEND_TEST(TestCaseName, TestName);
```
For example,
```
// foo.h
#include "gtest/gtest_prod.h"
// Defines FRIEND_TEST.
class Foo {
...
private:
FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
int Bar(void* x);
};
// foo_test.cc
...
TEST(FooTest, BarReturnsZeroOnNull) {
Foo foo;
EXPECT_EQ(0, foo.Bar(NULL));
// Uses Foo's private member Bar().
}
```
Pay special attention when your class is defined in a namespace, as you should
define your test fixtures and tests in the same namespace if you want them to
be friends of your class. For example, if the code to be tested looks like:
```
namespace my_namespace {
class Foo {
friend class FooTest;
FRIEND_TEST(FooTest, Bar);
FRIEND_TEST(FooTest, Baz);
...
definition of the class Foo
...
};
} // namespace my_namespace
```
Your test code should be something like:
```
namespace my_namespace {
class FooTest : public ::testing::Test {
protected:
...
};
TEST_F(FooTest, Bar) { ... }
TEST_F(FooTest, Baz) { ... }
} // namespace my_namespace
```
# Catching Failures #
If you are building a testing utility on top of Google Test, you'll
want to test your utility. What framework would you use to test it?
Google Test, of course.
The challenge is to verify that your testing utility reports failures
correctly. In frameworks that report a failure by throwing an
exception, you could catch the exception and assert on it. But Google
Test doesn't use exceptions, so how do we test that a piece of code
generates an expected failure?
`"gtest/gtest-spi.h"` contains some constructs to do this. After
`#include`ing this header, you can use
| `EXPECT_FATAL_FAILURE(`_statement, substring_`);` |
|:--------------------------------------------------|
to assert that _statement_ generates a fatal (e.g. `ASSERT_*`) failure
whose message contains the given _substring_, or use
| `EXPECT_NONFATAL_FAILURE(`_statement, substring_`);` |
|:-----------------------------------------------------|
if you are expecting a non-fatal (e.g. `EXPECT_*`) failure.
For technical reasons, there are some caveats:
1. You cannot stream a failure message to either macro.
1. _statement_ in `EXPECT_FATAL_FAILURE()` cannot reference local non-static variables or non-static members of `this` object.
1. _statement_ in `EXPECT_FATAL_FAILURE()` cannot return a value.
_Note:_ Google Test is designed with threads in mind. Once the
synchronization primitives in `"gtest/internal/gtest-port.h"` have
been implemented, Google Test will become thread-safe, meaning that
you can then use assertions in multiple threads concurrently. Before
that, however, Google Test only supports single-threaded usage. Once
thread-safe, `EXPECT_FATAL_FAILURE()` and `EXPECT_NONFATAL_FAILURE()`
will capture failures in the current thread only. If _statement_
creates new threads, failures in these threads will be ignored. If
you want to capture failures from all threads instead, you should use
the following macros:
| `EXPECT_FATAL_FAILURE_ON_ALL_THREADS(`_statement, substring_`);` |
|:-----------------------------------------------------------------|
| `EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(`_statement, substring_`);` |
# Getting the Current Test's Name #
Sometimes a function may need to know the name of the currently running test.
For example, you may be using the `SetUp()` method of your test fixture to set
the golden file name based on which test is running. The `::testing::TestInfo`
class has this information:
```
namespace testing {
class TestInfo {
public:
// Returns the test case name and the test name, respectively.
//
// Do NOT delete or free the return value - it's managed by the
// TestInfo class.
const char* test_case_name() const;
const char* name() const;
};
} // namespace testing
```
> To obtain a `TestInfo` object for the currently running test, call
`current_test_info()` on the `UnitTest` singleton object:
```
// Gets information about the currently running test.
// Do NOT delete the returned object - it's managed by the UnitTest class.
const ::testing::TestInfo* const test_info =
::testing::UnitTest::GetInstance()->current_test_info();
printf("We are in test %s of test case %s.\n",
test_info->name(), test_info->test_case_name());
```
`current_test_info()` returns a null pointer if no test is running. In
particular, you cannot find the test case name in `TestCaseSetUp()`,
`TestCaseTearDown()` (where you know the test case name implicitly), or
functions called from them.
_Availability:_ Linux, Windows, Mac.
# Extending Google Test by Handling Test Events #
Google Test provides an <b>event listener API</b> to let you receive
notifications about the progress of a test program and test
failures. The events you can listen to include the start and end of
the test program, a test case, or a test method, among others. You may
use this API to augment or replace the standard console output,
replace the XML output, or provide a completely different form of
output, such as a GUI or a database. You can also use test events as
checkpoints to implement a resource leak checker, for example.
_Availability:_ Linux, Windows, Mac; since v1.4.0.
## Defining Event Listeners ##
To define a event listener, you subclass either
[testing::TestEventListener](../include/gtest/gtest.h#L855)
or [testing::EmptyTestEventListener](../include/gtest/gtest.h#L905).
The former is an (abstract) interface, where <i>each pure virtual method<br>
can be overridden to handle a test event</i> (For example, when a test
starts, the `OnTestStart()` method will be called.). The latter provides
an empty implementation of all methods in the interface, such that a
subclass only needs to override the methods it cares about.
When an event is fired, its context is passed to the handler function
as an argument. The following argument types are used:
* [UnitTest](../include/gtest/gtest.h#L1007) reflects the state of the entire test program,
* [TestCase](../include/gtest/gtest.h#L689) has information about a test case, which can contain one or more tests,
* [TestInfo](../include/gtest/gtest.h#L599) contains the state of a test, and
* [TestPartResult](../include/gtest/gtest-test-part.h#L42) represents the result of a test assertion.
An event handler function can examine the argument it receives to find
out interesting information about the event and the test program's
state. Here's an example:
```
class MinimalistPrinter : public ::testing::EmptyTestEventListener {
// Called before a test starts.
virtual void OnTestStart(const ::testing::TestInfo& test_info) {
printf("*** Test %s.%s starting.\n",
test_info.test_case_name(), test_info.name());
}
// Called after a failed assertion or a SUCCEED() invocation.
virtual void OnTestPartResult(
const ::testing::TestPartResult& test_part_result) {
printf("%s in %s:%d\n%s\n",
test_part_result.failed() ? "*** Failure" : "Success",
test_part_result.file_name(),
test_part_result.line_number(),
test_part_result.summary());
}
// Called after a test ends.
virtual void OnTestEnd(const ::testing::TestInfo& test_info) {
printf("*** Test %s.%s ending.\n",
test_info.test_case_name(), test_info.name());
}
};
```
## Using Event Listeners ##
To use the event listener you have defined, add an instance of it to
the Google Test event listener list (represented by class
[TestEventListeners](../include/gtest/gtest.h#L929)
- note the "s" at the end of the name) in your
`main()` function, before calling `RUN_ALL_TESTS()`:
```
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
// Gets hold of the event listener list.
::testing::TestEventListeners& listeners =
::testing::UnitTest::GetInstance()->listeners();
// Adds a listener to the end. Google Test takes the ownership.
listeners.Append(new MinimalistPrinter);
return RUN_ALL_TESTS();
}
```
There's only one problem: the default test result printer is still in
effect, so its output will mingle with the output from your minimalist
printer. To suppress the default printer, just release it from the
event listener list and delete it. You can do so by adding one line:
```
...
delete listeners.Release(listeners.default_result_printer());
listeners.Append(new MinimalistPrinter);
return RUN_ALL_TESTS();
```
Now, sit back and enjoy a completely different output from your
tests. For more details, you can read this
[sample](../samples/sample9_unittest.cc).
You may append more than one listener to the list. When an `On*Start()`
or `OnTestPartResult()` event is fired, the listeners will receive it in
the order they appear in the list (since new listeners are added to
the end of the list, the default text printer and the default XML
generator will receive the event first). An `On*End()` event will be
received by the listeners in the _reverse_ order. This allows output by
listeners added later to be framed by output from listeners added
earlier.
## Generating Failures in Listeners ##
You may use failure-raising macros (`EXPECT_*()`, `ASSERT_*()`,
`FAIL()`, etc) when processing an event. There are some restrictions:
1. You cannot generate any failure in `OnTestPartResult()` (otherwise it will cause `OnTestPartResult()` to be called recursively).
1. A listener that handles `OnTestPartResult()` is not allowed to generate any failure.
When you add listeners to the listener list, you should put listeners
that handle `OnTestPartResult()` _before_ listeners that can generate
failures. This ensures that failures generated by the latter are
attributed to the right test by the former.
We have a sample of failure-raising listener
[here](../samples/sample10_unittest.cc).
# Running Test Programs: Advanced Options #
Google Test test programs are ordinary executables. Once built, you can run
them directly and affect their behavior via the following environment variables
and/or command line flags. For the flags to work, your programs must call
`::testing::InitGoogleTest()` before calling `RUN_ALL_TESTS()`.
To see a list of supported flags and their usage, please run your test
program with the `--help` flag. You can also use `-h`, `-?`, or `/?`
for short. This feature is added in version 1.3.0.
If an option is specified both by an environment variable and by a
flag, the latter takes precedence. Most of the options can also be
set/read in code: to access the value of command line flag
`--gtest_foo`, write `::testing::GTEST_FLAG(foo)`. A common pattern is
to set the value of a flag before calling `::testing::InitGoogleTest()`
to change the default value of the flag:
```
int main(int argc, char** argv) {
// Disables elapsed time by default.
::testing::GTEST_FLAG(print_time) = false;
// This allows the user to override the flag on the command line.
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
## Selecting Tests ##
This section shows various options for choosing which tests to run.
### Listing Test Names ###
Sometimes it is necessary to list the available tests in a program before
running them so that a filter may be applied if needed. Including the flag
`--gtest_list_tests` overrides all other flags and lists tests in the following
format:
```
TestCase1.
TestName1
TestName2
TestCase2.
TestName
```
None of the tests listed are actually run if the flag is provided. There is no
corresponding environment variable for this flag.
_Availability:_ Linux, Windows, Mac.
### Running a Subset of the Tests ###
By default, a Google Test program runs all tests the user has defined.
Sometimes, you want to run only a subset of the tests (e.g. for debugging or
quickly verifying a change). If you set the `GTEST_FILTER` environment variable
or the `--gtest_filter` flag to a filter string, Google Test will only run the
tests whose full names (in the form of `TestCaseName.TestName`) match the
filter.
The format of a filter is a '`:`'-separated list of wildcard patterns (called
the positive patterns) optionally followed by a '`-`' and another
'`:`'-separated pattern list (called the negative patterns). A test matches the
filter if and only if it matches any of the positive patterns but does not
match any of the negative patterns.
A pattern may contain `'*'` (matches any string) or `'?'` (matches any single
character). For convenience, the filter `'*-NegativePatterns'` can be also
written as `'-NegativePatterns'`.
For example:
* `./foo_test` Has no flag, and thus runs all its tests.
* `./foo_test --gtest_filter=*` Also runs everything, due to the single match-everything `*` value.
* `./foo_test --gtest_filter=FooTest.*` Runs everything in test case `FooTest`.
* `./foo_test --gtest_filter=*Null*:*Constructor*` Runs any test whose full name contains either `"Null"` or `"Constructor"`.
* `./foo_test --gtest_filter=-*DeathTest.*` Runs all non-death tests.
* `./foo_test --gtest_filter=FooTest.*-FooTest.Bar` Runs everything in test case `FooTest` except `FooTest.Bar`.
_Availability:_ Linux, Windows, Mac.
### Temporarily Disabling Tests ###
If you have a broken test that you cannot fix right away, you can add the
`DISABLED_` prefix to its name. This will exclude it from execution. This is
better than commenting out the code or using `#if 0`, as disabled tests are
still compiled (and thus won't rot).
If you need to disable all tests in a test case, you can either add `DISABLED_`
to the front of the name of each test, or alternatively add it to the front of
the test case name.
For example, the following tests won't be run by Google Test, even though they
will still be compiled:
```
// Tests that Foo does Abc.
TEST(FooTest, DISABLED_DoesAbc) { ... }
class DISABLED_BarTest : public ::testing::Test { ... };
// Tests that Bar does Xyz.
TEST_F(DISABLED_BarTest, DoesXyz) { ... }
```
_Note:_ This feature should only be used for temporary pain-relief. You still
have to fix the disabled tests at a later date. As a reminder, Google Test will
print a banner warning you if a test program contains any disabled tests.
_Tip:_ You can easily count the number of disabled tests you have
using `grep`. This number can be used as a metric for improving your
test quality.
_Availability:_ Linux, Windows, Mac.
### Temporarily Enabling Disabled Tests ###
To include [disabled tests](#temporarily-disabling-tests) in test
execution, just invoke the test program with the
`--gtest_also_run_disabled_tests` flag or set the
`GTEST_ALSO_RUN_DISABLED_TESTS` environment variable to a value other
than `0`. You can combine this with the
[--gtest\-filter](#running-a-subset-of-the_tests) flag to further select
which disabled tests to run.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
## Repeating the Tests ##
Once in a while you'll run into a test whose result is hit-or-miss. Perhaps it
will fail only 1% of the time, making it rather hard to reproduce the bug under
a debugger. This can be a major source of frustration.
The `--gtest_repeat` flag allows you to repeat all (or selected) test methods
in a program many times. Hopefully, a flaky test will eventually fail and give
you a chance to debug. Here's how to use it:
| `$ foo_test --gtest_repeat=1000` | Repeat foo\_test 1000 times and don't stop at failures. |
|:---------------------------------|:--------------------------------------------------------|
| `$ foo_test --gtest_repeat=-1` | A negative count means repeating forever. |
| `$ foo_test --gtest_repeat=1000 --gtest_break_on_failure` | Repeat foo\_test 1000 times, stopping at the first failure. This is especially useful when running under a debugger: when the testfails, it will drop into the debugger and you can then inspect variables and stacks. |
| `$ foo_test --gtest_repeat=1000 --gtest_filter=FooBar` | Repeat the tests whose name matches the filter 1000 times. |
If your test program contains global set-up/tear-down code registered
using `AddGlobalTestEnvironment()`, it will be repeated in each
iteration as well, as the flakiness may be in it. You can also specify
the repeat count by setting the `GTEST_REPEAT` environment variable.
_Availability:_ Linux, Windows, Mac.
## Shuffling the Tests ##
You can specify the `--gtest_shuffle` flag (or set the `GTEST_SHUFFLE`
environment variable to `1`) to run the tests in a program in a random
order. This helps to reveal bad dependencies between tests.
By default, Google Test uses a random seed calculated from the current
time. Therefore you'll get a different order every time. The console
output includes the random seed value, such that you can reproduce an
order-related test failure later. To specify the random seed
explicitly, use the `--gtest_random_seed=SEED` flag (or set the
`GTEST_RANDOM_SEED` environment variable), where `SEED` is an integer
between 0 and 99999. The seed value 0 is special: it tells Google Test
to do the default behavior of calculating the seed from the current
time.
If you combine this with `--gtest_repeat=N`, Google Test will pick a
different random seed and re-shuffle the tests in each iteration.
_Availability:_ Linux, Windows, Mac; since v1.4.0.
## Controlling Test Output ##
This section teaches how to tweak the way test results are reported.
### Colored Terminal Output ###
Google Test can use colors in its terminal output to make it easier to spot
the separation between tests, and whether tests passed.
You can set the GTEST\_COLOR environment variable or set the `--gtest_color`
command line flag to `yes`, `no`, or `auto` (the default) to enable colors,
disable colors, or let Google Test decide. When the value is `auto`, Google
Test will use colors if and only if the output goes to a terminal and (on
non-Windows platforms) the `TERM` environment variable is set to `xterm` or
`xterm-color`.
_Availability:_ Linux, Windows, Mac.
### Suppressing the Elapsed Time ###
By default, Google Test prints the time it takes to run each test. To
suppress that, run the test program with the `--gtest_print_time=0`
command line flag. Setting the `GTEST_PRINT_TIME` environment
variable to `0` has the same effect.
_Availability:_ Linux, Windows, Mac. (In Google Test 1.3.0 and lower,
the default behavior is that the elapsed time is **not** printed.)
### Generating an XML Report ###
Google Test can emit a detailed XML report to a file in addition to its normal
textual output. The report contains the duration of each test, and thus can
help you identify slow tests.
To generate the XML report, set the `GTEST_OUTPUT` environment variable or the
`--gtest_output` flag to the string `"xml:_path_to_output_file_"`, which will
create the file at the given location. You can also just use the string
`"xml"`, in which case the output can be found in the `test_detail.xml` file in
the current directory.
If you specify a directory (for example, `"xml:output/directory/"` on Linux or
`"xml:output\directory\"` on Windows), Google Test will create the XML file in
that directory, named after the test executable (e.g. `foo_test.xml` for test
program `foo_test` or `foo_test.exe`). If the file already exists (perhaps left
over from a previous run), Google Test will pick a different name (e.g.
`foo_test_1.xml`) to avoid overwriting it.
The report uses the format described here. It is based on the
`junitreport` Ant task and can be parsed by popular continuous build
systems like [Hudson](https://hudson.dev.java.net/). Since that format
was originally intended for Java, a little interpretation is required
to make it apply to Google Test tests, as shown here:
```
<testsuites name="AllTests" ...>
<testsuite name="test_case_name" ...>
<testcase name="test_name" ...>
<failure message="..."/>
<failure message="..."/>
<failure message="..."/>
</testcase>
</testsuite>
</testsuites>
```
* The root `<testsuites>` element corresponds to the entire test program.
* `<testsuite>` elements correspond to Google Test test cases.
* `<testcase>` elements correspond to Google Test test functions.
For instance, the following program
```
TEST(MathTest, Addition) { ... }
TEST(MathTest, Subtraction) { ... }
TEST(LogicTest, NonContradiction) { ... }
```
could generate this report:
```
<?xml version="1.0" encoding="UTF-8"?>
<testsuites tests="3" failures="1" errors="0" time="35" name="AllTests">
<testsuite name="MathTest" tests="2" failures="1" errors="0" time="15">
<testcase name="Addition" status="run" time="7" classname="">
<failure message="Value of: add(1, 1)&#x0A; Actual: 3&#x0A;Expected: 2" type=""/>
<failure message="Value of: add(1, -1)&#x0A; Actual: 1&#x0A;Expected: 0" type=""/>
</testcase>
<testcase name="Subtraction" status="run" time="5" classname="">
</testcase>
</testsuite>
<testsuite name="LogicTest" tests="1" failures="0" errors="0" time="5">
<testcase name="NonContradiction" status="run" time="5" classname="">
</testcase>
</testsuite>
</testsuites>
```
Things to note:
* The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how many test functions the Google Test program or test case contains, while the `failures` attribute tells how many of them failed.
* The `time` attribute expresses the duration of the test, test case, or entire test program in milliseconds.
* Each `<failure>` element corresponds to a single failed Google Test assertion.
* Some JUnit concepts don't apply to Google Test, yet we have to conform to the DTD. Therefore you'll see some dummy elements and attributes in the report. You can safely ignore these parts.
_Availability:_ Linux, Windows, Mac.
## Controlling How Failures Are Reported ##
### Turning Assertion Failures into Break-Points ###
When running test programs under a debugger, it's very convenient if the
debugger can catch an assertion failure and automatically drop into interactive
mode. Google Test's _break-on-failure_ mode supports this behavior.
To enable it, set the `GTEST_BREAK_ON_FAILURE` environment variable to a value
other than `0` . Alternatively, you can use the `--gtest_break_on_failure`
command line flag.
_Availability:_ Linux, Windows, Mac.
### Disabling Catching Test-Thrown Exceptions ###
Google Test can be used either with or without exceptions enabled. If
a test throws a C++ exception or (on Windows) a structured exception
(SEH), by default Google Test catches it, reports it as a test
failure, and continues with the next test method. This maximizes the
coverage of a test run. Also, on Windows an uncaught exception will
cause a pop-up window, so catching the exceptions allows you to run
the tests automatically.
When debugging the test failures, however, you may instead want the
exceptions to be handled by the debugger, such that you can examine
the call stack when an exception is thrown. To achieve that, set the
`GTEST_CATCH_EXCEPTIONS` environment variable to `0`, or use the
`--gtest_catch_exceptions=0` flag when running the tests.
**Availability**: Linux, Windows, Mac.
### Letting Another Testing Framework Drive ###
If you work on a project that has already been using another testing
framework and is not ready to completely switch to Google Test yet,
you can get much of Google Test's benefit by using its assertions in
your existing tests. Just change your `main()` function to look
like:
```
#include "gtest/gtest.h"
int main(int argc, char** argv) {
::testing::GTEST_FLAG(throw_on_failure) = true;
// Important: Google Test must be initialized.
::testing::InitGoogleTest(&argc, argv);
... whatever your existing testing framework requires ...
}
```
With that, you can use Google Test assertions in addition to the
native assertions your testing framework provides, for example:
```
void TestFooDoesBar() {
Foo foo;
EXPECT_LE(foo.Bar(1), 100); // A Google Test assertion.
CPPUNIT_ASSERT(foo.IsEmpty()); // A native assertion.
}
```
If a Google Test assertion fails, it will print an error message and
throw an exception, which will be treated as a failure by your host
testing framework. If you compile your code with exceptions disabled,
a failed Google Test assertion will instead exit your program with a
non-zero code, which will also signal a test failure to your test
runner.
If you don't write `::testing::GTEST_FLAG(throw_on_failure) = true;` in
your `main()`, you can alternatively enable this feature by specifying
the `--gtest_throw_on_failure` flag on the command-line or setting the
`GTEST_THROW_ON_FAILURE` environment variable to a non-zero value.
_Availability:_ Linux, Windows, Mac; since v1.3.0.
## Distributing Test Functions to Multiple Machines ##
If you have more than one machine you can use to run a test program,
you might want to run the test functions in parallel and get the
result faster. We call this technique _sharding_, where each machine
is called a _shard_.
Google Test is compatible with test sharding. To take advantage of
this feature, your test runner (not part of Google Test) needs to do
the following:
1. Allocate a number of machines (shards) to run the tests.
1. On each shard, set the `GTEST_TOTAL_SHARDS` environment variable to the total number of shards. It must be the same for all shards.
1. On each shard, set the `GTEST_SHARD_INDEX` environment variable to the index of the shard. Different shards must be assigned different indices, which must be in the range `[0, GTEST_TOTAL_SHARDS - 1]`.
1. Run the same test program on all shards. When Google Test sees the above two environment variables, it will select a subset of the test functions to run. Across all shards, each test function in the program will be run exactly once.
1. Wait for all shards to finish, then collect and report the results.
Your project may have tests that were written without Google Test and
thus don't understand this protocol. In order for your test runner to
figure out which test supports sharding, it can set the environment
variable `GTEST_SHARD_STATUS_FILE` to a non-existent file path. If a
test program supports sharding, it will create this file to
acknowledge the fact (the actual contents of the file are not
important at this time; although we may stick some useful information
in it in the future.); otherwise it will not create it.
Here's an example to make it clear. Suppose you have a test program
`foo_test` that contains the following 5 test functions:
```
TEST(A, V)
TEST(A, W)
TEST(B, X)
TEST(B, Y)
TEST(B, Z)
```
and you have 3 machines at your disposal. To run the test functions in
parallel, you would set `GTEST_TOTAL_SHARDS` to 3 on all machines, and
set `GTEST_SHARD_INDEX` to 0, 1, and 2 on the machines respectively.
Then you would run the same `foo_test` on each machine.
Google Test reserves the right to change how the work is distributed
across the shards, but here's one possible scenario:
* Machine #0 runs `A.V` and `B.X`.
* Machine #1 runs `A.W` and `B.Y`.
* Machine #2 runs `B.Z`.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
# Fusing Google Test Source Files #
Google Test's implementation consists of ~30 files (excluding its own
tests). Sometimes you may want them to be packaged up in two files (a
`.h` and a `.cc`) instead, such that you can easily copy them to a new
machine and start hacking there. For this we provide an experimental
Python script `fuse_gtest_files.py` in the `scripts/` directory (since release 1.3.0).
Assuming you have Python 2.4 or above installed on your machine, just
go to that directory and run
```
python fuse_gtest_files.py OUTPUT_DIR
```
and you should see an `OUTPUT_DIR` directory being created with files
`gtest/gtest.h` and `gtest/gtest-all.cc` in it. These files contain
everything you need to use Google Test. Just copy them to anywhere
you want and you are ready to write tests. You can use the
[scripts/test/Makefile](../scripts/test/Makefile)
file as an example on how to compile your tests against them.
# Where to Go from Here #
Congratulations! You've now learned more advanced Google Test tools and are
ready to tackle more complex testing tasks. If you want to dive even deeper, you
can read the [Frequently-Asked Questions](V1_6_FAQ.md).
googletest/docs/V1_6_Documentation.md deleted 100644 → 0
View file @ 15790643
This page lists all documentation wiki pages for Google Test **1.6**
-- **if you use a released version of Google Test, please read the
documentation for that specific version instead.**
* [Primer](V1_6_Primer.md) -- start here if you are new to Google Test.
* [Samples](V1_6_Samples.md) -- learn from examples.
* [AdvancedGuide](V1_6_AdvancedGuide.md) -- learn more about Google Test.
* [XcodeGuide](V1_6_XcodeGuide.md) -- how to use Google Test in Xcode on Mac.
* [Frequently-Asked Questions](V1_6_FAQ.md) -- check here before asking a question on the mailing list.
To contribute code to Google Test, read:
* [DevGuide](DevGuide.md) -- read this _before_ writing your first patch.
* [PumpManual](V1_6_PumpManual.md) -- how we generate some of Google Test's source files.
\ No newline at end of file
googletest/docs/V1_6_FAQ.md deleted 100644 → 0
View file @ 15790643
If you cannot find the answer to your question here, and you have read
[Primer](V1_6_Primer.md) and [AdvancedGuide](V1_6_AdvancedGuide.md), send it to
googletestframework@googlegroups.com.
## Why should I use Google Test instead of my favorite C++ testing framework? ##
First, let us say clearly that we don't want to get into the debate of
which C++ testing framework is **the best**. There exist many fine
frameworks for writing C++ tests, and we have tremendous respect for
the developers and users of them. We don't think there is (or will
be) a single best framework - you have to pick the right tool for the
particular task you are tackling.
We created Google Test because we couldn't find the right combination
of features and conveniences in an existing framework to satisfy _our_
needs. The following is a list of things that _we_ like about Google
Test. We don't claim them to be unique to Google Test - rather, the
combination of them makes Google Test the choice for us. We hope this
list can help you decide whether it is for you too.
* Google Test is designed to be portable: it doesn't require exceptions or RTTI; it works around various bugs in various compilers and environments; etc. As a result, it works on Linux, Mac OS X, Windows and several embedded operating systems.
* Nonfatal assertions (`EXPECT_*`) have proven to be great time savers, as they allow a test to report multiple failures in a single edit-compile-test cycle.
* It's easy to write assertions that generate informative messages: you just use the stream syntax to append any additional information, e.g. `ASSERT_EQ(5, Foo(i)) << " where i = " << i;`. It doesn't require a new set of macros or special functions.
* Google Test automatically detects your tests and doesn't require you to enumerate them in order to run them.
* Death tests are pretty handy for ensuring that your asserts in production code are triggered by the right conditions.
* `SCOPED_TRACE` helps you understand the context of an assertion failure when it comes from inside a sub-routine or loop.
* You can decide which tests to run using name patterns. This saves time when you want to quickly reproduce a test failure.
* Google Test can generate XML test result reports that can be parsed by popular continuous build system like Hudson.
* Simple things are easy in Google Test, while hard things are possible: in addition to advanced features like [global test environments](V1_6_AdvancedGuide.md#Global_Set-Up_and_Tear-Down) and tests parameterized by [values](V1_6_AdvancedGuide.md#value-parameterized-tests) or [types](V1_6_AdvancedGuide.md#typed-tests), Google Test supports various ways for the user to extend the framework -- if Google Test doesn't do something out of the box, chances are that a user can implement the feature using Google Test's public API, without changing Google Test itself. In particular, you can:
* expand your testing vocabulary by defining [custom predicates](V1_6_AdvancedGuide.md#predicate-assertions-for-better-error-messages),
* teach Google Test how to [print your types](V1_6_AdvancedGuide.md#teaching-google-test-how-to-print-your-values),
* define your own testing macros or utilities and verify them using Google Test's [Service Provider Interface](V1_6_AdvancedGuide.md#catching-failures), and
* reflect on the test cases or change the test output format by intercepting the [test events](V1_6_AdvancedGuide.md#extending-google-test-by-handling-test-events).
## I'm getting warnings when compiling Google Test. Would you fix them? ##
We strive to minimize compiler warnings Google Test generates. Before releasing a new version, we test to make sure that it doesn't generate warnings when compiled using its CMake script on Windows, Linux, and Mac OS.
Unfortunately, this doesn't mean you are guaranteed to see no warnings when compiling Google Test in your environment:
* You may be using a different compiler as we use, or a different version of the same compiler. We cannot possibly test for all compilers.
* You may be compiling on a different platform as we do.
* Your project may be using different compiler flags as we do.
It is not always possible to make Google Test warning-free for everyone. Or, it may not be desirable if the warning is rarely enabled and fixing the violations makes the code more complex.
If you see warnings when compiling Google Test, we suggest that you use the `-isystem` flag (assuming your are using GCC) to mark Google Test headers as system headers. That'll suppress warnings from Google Test headers.
## Why should not test case names and test names contain underscore? ##
Underscore (`_`) is special, as C++ reserves the following to be used by
the compiler and the standard library:
1. any identifier that starts with an `_` followed by an upper-case letter, and
1. any identifier that containers two consecutive underscores (i.e. `__`) _anywhere_ in its name.
User code is _prohibited_ from using such identifiers.
Now let's look at what this means for `TEST` and `TEST_F`.
Currently `TEST(TestCaseName, TestName)` generates a class named
`TestCaseName_TestName_Test`. What happens if `TestCaseName` or `TestName`
contains `_`?
1. If `TestCaseName` starts with an `_` followed by an upper-case letter (say, `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus invalid.
1. If `TestCaseName` ends with an `_` (say, `Foo_`), we get `Foo__TestName_Test`, which is invalid.
1. If `TestName` starts with an `_` (say, `_Bar`), we get `TestCaseName__Bar_Test`, which is invalid.
1. If `TestName` ends with an `_` (say, `Bar_`), we get `TestCaseName_Bar__Test`, which is invalid.
So clearly `TestCaseName` and `TestName` cannot start or end with `_`
(Actually, `TestCaseName` can start with `_` -- as long as the `_` isn't
followed by an upper-case letter. But that's getting complicated. So
for simplicity we just say that it cannot start with `_`.).
It may seem fine for `TestCaseName` and `TestName` to contain `_` in the
middle. However, consider this:
```
TEST(Time, Flies_Like_An_Arrow) { ... }
TEST(Time_Flies, Like_An_Arrow) { ... }
```
Now, the two `TEST`s will both generate the same class
(`Time_Files_Like_An_Arrow_Test`). That's not good.
So for simplicity, we just ask the users to avoid `_` in `TestCaseName`
and `TestName`. The rule is more constraining than necessary, but it's
simple and easy to remember. It also gives Google Test some wiggle
room in case its implementation needs to change in the future.
If you violate the rule, there may not be immediately consequences,
but your test may (just may) break with a new compiler (or a new
version of the compiler you are using) or with a new version of Google
Test. Therefore it's best to follow the rule.
## Why is it not recommended to install a pre-compiled copy of Google Test (for example, into /usr/local)? ##
In the early days, we said that you could install
compiled Google Test libraries on `*`nix systems using `make install`.
Then every user of your machine can write tests without
recompiling Google Test.
This seemed like a good idea, but it has a
got-cha: every user needs to compile his tests using the _same_ compiler
flags used to compile the installed Google Test libraries; otherwise
he may run into undefined behaviors (i.e. the tests can behave
strangely and may even crash for no obvious reasons).
Why? Because C++ has this thing called the One-Definition Rule: if
two C++ source files contain different definitions of the same
class/function/variable, and you link them together, you violate the
rule. The linker may or may not catch the error (in many cases it's
not required by the C++ standard to catch the violation). If it
doesn't, you get strange run-time behaviors that are unexpected and
hard to debug.
If you compile Google Test and your test code using different compiler
flags, they may see different definitions of the same
class/function/variable (e.g. due to the use of `#if` in Google Test).
Therefore, for your sanity, we recommend to avoid installing pre-compiled
Google Test libraries. Instead, each project should compile
Google Test itself such that it can be sure that the same flags are
used for both Google Test and the tests.
## How do I generate 64-bit binaries on Windows (using Visual Studio 2008)? ##
(Answered by Trevor Robinson)
Load the supplied Visual Studio solution file, either `msvc\gtest-md.sln` or
`msvc\gtest.sln`. Go through the migration wizard to migrate the
solution and project files to Visual Studio 2008. Select
`Configuration Manager...` from the `Build` menu. Select `<New...>` from
the `Active solution platform` dropdown. Select `x64` from the new
platform dropdown, leave `Copy settings from` set to `Win32` and
`Create new project platforms` checked, then click `OK`. You now have
`Win32` and `x64` platform configurations, selectable from the
`Standard` toolbar, which allow you to toggle between building 32-bit or
64-bit binaries (or both at once using Batch Build).
In order to prevent build output files from overwriting one another,
you'll need to change the `Intermediate Directory` settings for the
newly created platform configuration across all the projects. To do
this, multi-select (e.g. using shift-click) all projects (but not the
solution) in the `Solution Explorer`. Right-click one of them and
select `Properties`. In the left pane, select `Configuration Properties`,
and from the `Configuration` dropdown, select `All Configurations`.
Make sure the selected platform is `x64`. For the
`Intermediate Directory` setting, change the value from
`$(PlatformName)\$(ConfigurationName)` to
`$(OutDir)\$(ProjectName)`. Click `OK` and then build the
solution. When the build is complete, the 64-bit binaries will be in
the `msvc\x64\Debug` directory.
## Can I use Google Test on MinGW? ##
We haven't tested this ourselves, but Per Abrahamsen reported that he
was able to compile and install Google Test successfully when using
MinGW from Cygwin. You'll need to configure it with:
`PATH/TO/configure CC="gcc -mno-cygwin" CXX="g++ -mno-cygwin"`
You should be able to replace the `-mno-cygwin` option with direct links
to the real MinGW binaries, but we haven't tried that.
Caveats:
* There are many warnings when compiling.
* `make check` will produce some errors as not all tests for Google Test itself are compatible with MinGW.
We also have reports on successful cross compilation of Google Test
MinGW binaries on Linux using
[these instructions](http://wiki.wxwidgets.org/Cross-Compiling_Under_Linux#Cross-compiling_under_Linux_for_MS_Windows)
on the WxWidgets site.
Please contact `googletestframework@googlegroups.com` if you are
interested in improving the support for MinGW.
## Why does Google Test support EXPECT\_EQ(NULL, ptr) and ASSERT\_EQ(NULL, ptr) but not EXPECT\_NE(NULL, ptr) and ASSERT\_NE(NULL, ptr)? ##
Due to some peculiarity of C++, it requires some non-trivial template
meta programming tricks to support using `NULL` as an argument of the
`EXPECT_XX()` and `ASSERT_XX()` macros. Therefore we only do it where
it's most needed (otherwise we make the implementation of Google Test
harder to maintain and more error-prone than necessary).
The `EXPECT_EQ()` macro takes the _expected_ value as its first
argument and the _actual_ value as the second. It's reasonable that
someone wants to write `EXPECT_EQ(NULL, some_expression)`, and this
indeed was requested several times. Therefore we implemented it.
The need for `EXPECT_NE(NULL, ptr)` isn't nearly as strong. When the
assertion fails, you already know that `ptr` must be `NULL`, so it
doesn't add any information to print ptr in this case. That means
`EXPECT_TRUE(ptr ! NULL)` works just as well.
If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'll
have to support `EXPECT_NE(ptr, NULL)` as well, as unlike `EXPECT_EQ`,
we don't have a convention on the order of the two arguments for
`EXPECT_NE`. This means using the template meta programming tricks
twice in the implementation, making it even harder to understand and
maintain. We believe the benefit doesn't justify the cost.
Finally, with the growth of Google Mock's [matcher](../../CookBook.md#using-matchers-in-google-test-assertions) library, we are
encouraging people to use the unified `EXPECT_THAT(value, matcher)`
syntax more often in tests. One significant advantage of the matcher
approach is that matchers can be easily combined to form new matchers,
while the `EXPECT_NE`, etc, macros cannot be easily
combined. Therefore we want to invest more in the matchers than in the
`EXPECT_XX()` macros.
## Does Google Test support running tests in parallel? ##
Test runners tend to be tightly coupled with the build/test
environment, and Google Test doesn't try to solve the problem of
running tests in parallel. Instead, we tried to make Google Test work
nicely with test runners. For example, Google Test's XML report
contains the time spent on each test, and its `gtest_list_tests` and
`gtest_filter` flags can be used for splitting the execution of test
methods into multiple processes. These functionalities can help the
test runner run the tests in parallel.
## Why don't Google Test run the tests in different threads to speed things up? ##
It's difficult to write thread-safe code. Most tests are not written
with thread-safety in mind, and thus may not work correctly in a
multi-threaded setting.
If you think about it, it's already hard to make your code work when
you know what other threads are doing. It's much harder, and
sometimes even impossible, to make your code work when you don't know
what other threads are doing (remember that test methods can be added,
deleted, or modified after your test was written). If you want to run
the tests in parallel, you'd better run them in different processes.
## Why aren't Google Test assertions implemented using exceptions? ##
Our original motivation was to be able to use Google Test in projects
that disable exceptions. Later we realized some additional benefits
of this approach:
1. Throwing in a destructor is undefined behavior in C++. Not using exceptions means Google Test's assertions are safe to use in destructors.
1. The `EXPECT_*` family of macros will continue even after a failure, allowing multiple failures in a `TEST` to be reported in a single run. This is a popular feature, as in C++ the edit-compile-test cycle is usually quite long and being able to fixing more than one thing at a time is a blessing.
1. If assertions are implemented using exceptions, a test may falsely ignore a failure if it's caught by user code:
```
try { ... ASSERT_TRUE(...) ... }
catch (...) { ... }
```
The above code will pass even if the `ASSERT_TRUE` throws. While it's unlikely for someone to write this in a test, it's possible to run into this pattern when you write assertions in callbacks that are called by the code under test.
The downside of not using exceptions is that `ASSERT_*` (implemented
using `return`) will only abort the current function, not the current
`TEST`.
## Why do we use two different macros for tests with and without fixtures? ##
Unfortunately, C++'s macro system doesn't allow us to use the same
macro for both cases. One possibility is to provide only one macro
for tests with fixtures, and require the user to define an empty
fixture sometimes:
```
class FooTest : public ::testing::Test {};
TEST_F(FooTest, DoesThis) { ... }
```
or
```
typedef ::testing::Test FooTest;
TEST_F(FooTest, DoesThat) { ... }
```
Yet, many people think this is one line too many. :-) Our goal was to
make it really easy to write tests, so we tried to make simple tests
trivial to create. That means using a separate macro for such tests.
We think neither approach is ideal, yet either of them is reasonable.
In the end, it probably doesn't matter much either way.
## Why don't we use structs as test fixtures? ##
We like to use structs only when representing passive data. This
distinction between structs and classes is good for documenting the
intent of the code's author. Since test fixtures have logic like
`SetUp()` and `TearDown()`, they are better defined as classes.
## Why are death tests implemented as assertions instead of using a test runner? ##
Our goal was to make death tests as convenient for a user as C++
possibly allows. In particular:
* The runner-style requires to split the information into two pieces: the definition of the death test itself, and the specification for the runner on how to run the death test and what to expect. The death test would be written in C++, while the runner spec may or may not be. A user needs to carefully keep the two in sync. `ASSERT_DEATH(statement, expected_message)` specifies all necessary information in one place, in one language, without boilerplate code. It is very declarative.
* `ASSERT_DEATH` has a similar syntax and error-reporting semantics as other Google Test assertions, and thus is easy to learn.
* `ASSERT_DEATH` can be mixed with other assertions and other logic at your will. You are not limited to one death test per test method. For example, you can write something like:
```
if (FooCondition()) {
ASSERT_DEATH(Bar(), "blah");
} else {
ASSERT_EQ(5, Bar());
}
```
If you prefer one death test per test method, you can write your tests in that style too, but we don't want to impose that on the users. The fewer artificial limitations the better.
* `ASSERT_DEATH` can reference local variables in the current function, and you can decide how many death tests you want based on run-time information. For example,
```
const int count = GetCount(); // Only known at run time.
for (int i = 1; i <= count; i++) {
ASSERT_DEATH({
double* buffer = new double[i];
... initializes buffer ...
Foo(buffer, i)
}, "blah blah");
}
```
The runner-based approach tends to be more static and less flexible, or requires more user effort to get this kind of flexibility.
Another interesting thing about `ASSERT_DEATH` is that it calls `fork()`
to create a child process to run the death test. This is lightening
fast, as `fork()` uses copy-on-write pages and incurs almost zero
overhead, and the child process starts from the user-supplied
statement directly, skipping all global and local initialization and
any code leading to the given statement. If you launch the child
process from scratch, it can take seconds just to load everything and
start running if the test links to many libraries dynamically.
## My death test modifies some state, but the change seems lost after the death test finishes. Why? ##
Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
expected crash won't kill the test program (i.e. the parent process). As a
result, any in-memory side effects they incur are observable in their
respective sub-processes, but not in the parent process. You can think of them
as running in a parallel universe, more or less.
## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong? ##
If your class has a static data member:
```
// foo.h
class Foo {
...
static const int kBar = 100;
};
```
You also need to define it _outside_ of the class body in `foo.cc`:
```
const int Foo::kBar; // No initializer here.
```
Otherwise your code is **invalid C++**, and may break in unexpected ways. In
particular, using it in Google Test comparison assertions (`EXPECT_EQ`, etc)
will generate an "undefined reference" linker error.
## I have an interface that has several implementations. Can I write a set of tests once and repeat them over all the implementations? ##
Google Test doesn't yet have good support for this kind of tests, or
data-driven tests in general. We hope to be able to make improvements in this
area soon.
## Can I derive a test fixture from another? ##
Yes.
Each test fixture has a corresponding and same named test case. This means only
one test case can use a particular fixture. Sometimes, however, multiple test
cases may want to use the same or slightly different fixtures. For example, you
may want to make sure that all of a GUI library's test cases don't leak
important system resources like fonts and brushes.
In Google Test, you share a fixture among test cases by putting the shared
logic in a base test fixture, then deriving from that base a separate fixture
for each test case that wants to use this common logic. You then use `TEST_F()`
to write tests using each derived fixture.
Typically, your code looks like this:
```
// Defines a base test fixture.
class BaseTest : public ::testing::Test {
protected:
...
};
// Derives a fixture FooTest from BaseTest.
class FooTest : public BaseTest {
protected:
virtual void SetUp() {
BaseTest::SetUp(); // Sets up the base fixture first.
... additional set-up work ...
}
virtual void TearDown() {
... clean-up work for FooTest ...
BaseTest::TearDown(); // Remember to tear down the base fixture
// after cleaning up FooTest!
}
... functions and variables for FooTest ...
};
// Tests that use the fixture FooTest.
TEST_F(FooTest, Bar) { ... }
TEST_F(FooTest, Baz) { ... }
... additional fixtures derived from BaseTest ...
```
If necessary, you can continue to derive test fixtures from a derived fixture.
Google Test has no limit on how deep the hierarchy can be.
For a complete example using derived test fixtures, see
[sample5](../samples/sample5_unittest.cc).
## My compiler complains "void value not ignored as it ought to be." What does this mean? ##
You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
`ASSERT_*()` can only be used in `void` functions.
## My death test hangs (or seg-faults). How do I fix it? ##
In Google Test, death tests are run in a child process and the way they work is
delicate. To write death tests you really need to understand how they work.
Please make sure you have read this.
In particular, death tests don't like having multiple threads in the parent
process. So the first thing you can try is to eliminate creating threads
outside of `EXPECT_DEATH()`.
Sometimes this is impossible as some library you must use may be creating
threads before `main()` is even reached. In this case, you can try to minimize
the chance of conflicts by either moving as many activities as possible inside
`EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
leaving as few things as possible in it. Also, you can try to set the death
test style to `"threadsafe"`, which is safer but slower, and see if it helps.
If you go with thread-safe death tests, remember that they rerun the test
program from the beginning in the child process. Therefore make sure your
program can run side-by-side with itself and is deterministic.
In the end, this boils down to good concurrent programming. You have to make
sure that there is no race conditions or dead locks in your program. No silver
bullet - sorry!
## Should I use the constructor/destructor of the test fixture or the set-up/tear-down function? ##
The first thing to remember is that Google Test does not reuse the
same test fixture object across multiple tests. For each `TEST_F`,
Google Test will create a fresh test fixture object, _immediately_
call `SetUp()`, run the test, call `TearDown()`, and then
_immediately_ delete the test fixture object. Therefore, there is no
need to write a `SetUp()` or `TearDown()` function if the constructor
or destructor already does the job.
You may still want to use `SetUp()/TearDown()` in the following cases:
* If the tear-down operation could throw an exception, you must use `TearDown()` as opposed to the destructor, as throwing in a destructor leads to undefined behavior and usually will kill your program right away. Note that many standard libraries (like STL) may throw when exceptions are enabled in the compiler. Therefore you should prefer `TearDown()` if you want to write portable tests that work with or without exceptions.
* The Google Test team is considering making the assertion macros throw on platforms where exceptions are enabled (e.g. Windows, Mac OS, and Linux client-side), which will eliminate the need for the user to propagate failures from a subroutine to its caller. Therefore, you shouldn't use Google Test assertions in a destructor if your code could run on such a platform.
* In a constructor or destructor, you cannot make a virtual function call on this object. (You can call a method declared as virtual, but it will be statically bound.) Therefore, if you need to call a method that will be overriden in a derived class, you have to use `SetUp()/TearDown()`.
## The compiler complains "no matching function to call" when I use ASSERT\_PREDn. How do I fix it? ##
If the predicate function you use in `ASSERT_PRED*` or `EXPECT_PRED*` is
overloaded or a template, the compiler will have trouble figuring out which
overloaded version it should use. `ASSERT_PRED_FORMAT*` and
`EXPECT_PRED_FORMAT*` don't have this problem.
If you see this error, you might want to switch to
`(ASSERT|EXPECT)_PRED_FORMAT*`, which will also give you a better failure
message. If, however, that is not an option, you can resolve the problem by
explicitly telling the compiler which version to pick.
For example, suppose you have
```
bool IsPositive(int n) {
return n > 0;
}
bool IsPositive(double x) {
return x > 0;
}
```
you will get a compiler error if you write
```
EXPECT_PRED1(IsPositive, 5);
```
However, this will work:
```
EXPECT_PRED1(*static_cast<bool (*)(int)>*(IsPositive), 5);
```
(The stuff inside the angled brackets for the `static_cast` operator is the
type of the function pointer for the `int`-version of `IsPositive()`.)
As another example, when you have a template function
```
template <typename T>
bool IsNegative(T x) {
return x < 0;
}
```
you can use it in a predicate assertion like this:
```
ASSERT_PRED1(IsNegative*<int>*, -5);
```
Things are more interesting if your template has more than one parameters. The
following won't compile:
```
ASSERT_PRED2(*GreaterThan<int, int>*, 5, 0);
```
as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments,
which is one more than expected. The workaround is to wrap the predicate
function in parentheses:
```
ASSERT_PRED2(*(GreaterThan<int, int>)*, 5, 0);
```
## My compiler complains about "ignoring return value" when I call RUN\_ALL\_TESTS(). Why? ##
Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
instead of
```
return RUN_ALL_TESTS();
```
they write
```
RUN_ALL_TESTS();
```
This is wrong and dangerous. A test runner needs to see the return value of
`RUN_ALL_TESTS()` in order to determine if a test has passed. If your `main()`
function ignores it, your test will be considered successful even if it has a
Google Test assertion failure. Very bad.
To help the users avoid this dangerous bug, the implementation of
`RUN_ALL_TESTS()` causes gcc to raise this warning, when the return value is
ignored. If you see this warning, the fix is simple: just make sure its value
is used as the return value of `main()`.
## My compiler complains that a constructor (or destructor) cannot return a value. What's going on? ##
Due to a peculiarity of C++, in order to support the syntax for streaming
messages to an `ASSERT_*`, e.g.
```
ASSERT_EQ(1, Foo()) << "blah blah" << foo;
```
we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
`ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
content of your constructor/destructor to a private void member function, or
switch to `EXPECT_*()` if that works. This section in the user's guide explains
it.
## My set-up function is not called. Why? ##
C++ is case-sensitive. It should be spelled as `SetUp()`. Did you
spell it as `Setup()`?
Similarly, sometimes people spell `SetUpTestCase()` as `SetupTestCase()` and
wonder why it's never called.
## How do I jump to the line of a failure in Emacs directly? ##
Google Test's failure message format is understood by Emacs and many other
IDEs, like acme and XCode. If a Google Test message is in a compilation buffer
in Emacs, then it's clickable. You can now hit `enter` on a message to jump to
the corresponding source code, or use `C-x `` to jump to the next failure.
## I have several test cases which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious. ##
You don't have to. Instead of
```
class FooTest : public BaseTest {};
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
class BarTest : public BaseTest {};
TEST_F(BarTest, Abc) { ... }
TEST_F(BarTest, Def) { ... }
```
you can simply `typedef` the test fixtures:
```
typedef BaseTest FooTest;
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
typedef BaseTest BarTest;
TEST_F(BarTest, Abc) { ... }
TEST_F(BarTest, Def) { ... }
```
## The Google Test output is buried in a whole bunch of log messages. What do I do? ##
The Google Test output is meant to be a concise and human-friendly report. If
your test generates textual output itself, it will mix with the Google Test
output, making it hard to read. However, there is an easy solution to this
problem.
Since most log messages go to stderr, we decided to let Google Test output go
to stdout. This way, you can easily separate the two using redirection. For
example:
```
./my_test > googletest_output.txt
```
## Why should I prefer test fixtures over global variables? ##
There are several good reasons:
1. It's likely your test needs to change the states of its global variables. This makes it difficult to keep side effects from escaping one test and contaminating others, making debugging difficult. By using fixtures, each test has a fresh set of variables that's different (but with the same names). Thus, tests are kept independent of each other.
1. Global variables pollute the global namespace.
1. Test fixtures can be reused via subclassing, which cannot be done easily with global variables. This is useful if many test cases have something in common.
## How do I test private class members without writing FRIEND\_TEST()s? ##
You should try to write testable code, which means classes should be easily
tested from their public interface. One way to achieve this is the Pimpl idiom:
you move all private members of a class into a helper class, and make all
members of the helper class public.
You have several other options that don't require using `FRIEND_TEST`:
* Write the tests as members of the fixture class:
```
class Foo {
friend class FooTest;
...
};
class FooTest : public ::testing::Test {
protected:
...
void Test1() {...} // This accesses private members of class Foo.
void Test2() {...} // So does this one.
};
TEST_F(FooTest, Test1) {
Test1();
}
TEST_F(FooTest, Test2) {
Test2();
}
```
* In the fixture class, write accessors for the tested class' private members, then use the accessors in your tests:
```
class Foo {
friend class FooTest;
...
};
class FooTest : public ::testing::Test {
protected:
...
T1 get_private_member1(Foo* obj) {
return obj->private_member1_;
}
};
TEST_F(FooTest, Test1) {
...
get_private_member1(x)
...
}
```
* If the methods are declared **protected**, you can change their access level in a test-only subclass:
```
class YourClass {
...
protected: // protected access for testability.
int DoSomethingReturningInt();
...
};
// in the your_class_test.cc file:
class TestableYourClass : public YourClass {
...
public: using YourClass::DoSomethingReturningInt; // changes access rights
...
};
TEST_F(YourClassTest, DoSomethingTest) {
TestableYourClass obj;
assertEquals(expected_value, obj.DoSomethingReturningInt());
}
```
## How do I test private class static members without writing FRIEND\_TEST()s? ##
We find private static methods clutter the header file. They are
implementation details and ideally should be kept out of a .h. So often I make
them free functions instead.
Instead of:
```
// foo.h
class Foo {
...
private:
static bool Func(int n);
};
// foo.cc
bool Foo::Func(int n) { ... }
// foo_test.cc
EXPECT_TRUE(Foo::Func(12345));
```
You probably should better write:
```
// foo.h
class Foo {
...
};
// foo.cc
namespace internal {
bool Func(int n) { ... }
}
// foo_test.cc
namespace internal {
bool Func(int n);
}
EXPECT_TRUE(internal::Func(12345));
```
## I would like to run a test several times with different parameters. Do I need to write several similar copies of it? ##
No. You can use a feature called [value-parameterized tests](V1_6_AdvancedGuide.md#Value_Parameterized_Tests) which
lets you repeat your tests with different parameters, without defining it more than once.
## How do I test a file that defines main()? ##
To test a `foo.cc` file, you need to compile and link it into your unit test
program. However, when the file contains a definition for the `main()`
function, it will clash with the `main()` of your unit test, and will result in
a build error.
The right solution is to split it into three files:
1. `foo.h` which contains the declarations,
1. `foo.cc` which contains the definitions except `main()`, and
1. `foo_main.cc` which contains nothing but the definition of `main()`.
Then `foo.cc` can be easily tested.
If you are adding tests to an existing file and don't want an intrusive change
like this, there is a hack: just include the entire `foo.cc` file in your unit
test. For example:
```
// File foo_unittest.cc
// The headers section
...
// Renames main() in foo.cc to make room for the unit test main()
#define main FooMain
#include "a/b/foo.cc"
// The tests start here.
...
```
However, please remember this is a hack and should only be used as the last
resort.
## What can the statement argument in ASSERT\_DEATH() be? ##
`ASSERT_DEATH(_statement_, _regex_)` (or any death assertion macro) can be used
wherever `_statement_` is valid. So basically `_statement_` can be any C++
statement that makes sense in the current context. In particular, it can
reference global and/or local variables, and can be:
* a simple function call (often the case),
* a complex expression, or
* a compound statement.
> Some examples are shown here:
```
// A death test can be a simple function call.
TEST(MyDeathTest, FunctionCall) {
ASSERT_DEATH(Xyz(5), "Xyz failed");
}
// Or a complex expression that references variables and functions.
TEST(MyDeathTest, ComplexExpression) {
const bool c = Condition();
ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
"(Func1|Method) failed");
}
// Death assertions can be used any where in a function. In
// particular, they can be inside a loop.
TEST(MyDeathTest, InsideLoop) {
// Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
for (int i = 0; i < 5; i++) {
EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
::testing::Message() << "where i is " << i);
}
}
// A death assertion can contain a compound statement.
TEST(MyDeathTest, CompoundStatement) {
// Verifies that at lease one of Bar(0), Bar(1), ..., and
// Bar(4) dies.
ASSERT_DEATH({
for (int i = 0; i < 5; i++) {
Bar(i);
}
},
"Bar has \\d+ errors");}
```
`googletest_unittest.cc` contains more examples if you are interested.
## What syntax does the regular expression in ASSERT\_DEATH use? ##
On POSIX systems, Google Test uses the POSIX Extended regular
expression syntax
(http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions).
On Windows, it uses a limited variant of regular expression
syntax. For more details, see the
[regular expression syntax](V1_6_AdvancedGuide.md#Regular_Expression_Syntax).
## I have a fixture class Foo, but TEST\_F(Foo, Bar) gives me error "no matching function for call to Foo::Foo()". Why? ##
Google Test needs to be able to create objects of your test fixture class, so
it must have a default constructor. Normally the compiler will define one for
you. However, there are cases where you have to define your own:
* If you explicitly declare a non-default constructor for class `Foo`, then you need to define a default constructor, even if it would be empty.
* If `Foo` has a const non-static data member, then you have to define the default constructor _and_ initialize the const member in the initializer list of the constructor. (Early versions of `gcc` doesn't force you to initialize the const member. It's a bug that has been fixed in `gcc 4`.)
## Why does ASSERT\_DEATH complain about previous threads that were already joined? ##
With the Linux pthread library, there is no turning back once you cross the
line from single thread to multiple threads. The first time you create a
thread, a manager thread is created in addition, so you get 3, not 2, threads.
Later when the thread you create joins the main thread, the thread count
decrements by 1, but the manager thread will never be killed, so you still have
2 threads, which means you cannot safely run a death test.
The new NPTL thread library doesn't suffer from this problem, as it doesn't
create a manager thread. However, if you don't control which machine your test
runs on, you shouldn't depend on this.
## Why does Google Test require the entire test case, instead of individual tests, to be named FOODeathTest when it uses ASSERT\_DEATH? ##
Google Test does not interleave tests from different test cases. That is, it
runs all tests in one test case first, and then runs all tests in the next test
case, and so on. Google Test does this because it needs to set up a test case
before the first test in it is run, and tear it down afterwords. Splitting up
the test case would require multiple set-up and tear-down processes, which is
inefficient and makes the semantics unclean.
If we were to determine the order of tests based on test name instead of test
case name, then we would have a problem with the following situation:
```
TEST_F(FooTest, AbcDeathTest) { ... }
TEST_F(FooTest, Uvw) { ... }
TEST_F(BarTest, DefDeathTest) { ... }
TEST_F(BarTest, Xyz) { ... }
```
Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
interleave tests from different test cases, we need to run all tests in the
`FooTest` case before running any test in the `BarTest` case. This contradicts
with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
## But I don't like calling my entire test case FOODeathTest when it contains both death tests and non-death tests. What do I do? ##
You don't have to, but if you like, you may split up the test case into
`FooTest` and `FooDeathTest`, where the names make it clear that they are
related:
```
class FooTest : public ::testing::Test { ... };
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
typedef FooTest FooDeathTest;
TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
```
## The compiler complains about "no match for 'operator<<'" when I use an assertion. What gives? ##
If you use a user-defined type `FooType` in an assertion, you must make sure
there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
defined such that we can print a value of `FooType`.
In addition, if `FooType` is declared in a name space, the `<<` operator also
needs to be defined in the _same_ name space.
## How do I suppress the memory leak messages on Windows? ##
Since the statically initialized Google Test singleton requires allocations on
the heap, the Visual C++ memory leak detector will report memory leaks at the
end of the program run. The easiest way to avoid this is to use the
`_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
statically initialized heap objects. See MSDN for more details and additional
heap check/debug routines.
## I am building my project with Google Test in Visual Studio and all I'm getting is a bunch of linker errors (or warnings). Help! ##
You may get a number of the following linker error or warnings if you
attempt to link your test project with the Google Test library when
your project and the are not built using the same compiler settings.
* LNK2005: symbol already defined in object
* LNK4217: locally defined symbol 'symbol' imported in function 'function'
* LNK4049: locally defined symbol 'symbol' imported
The Google Test project (gtest.vcproj) has the Runtime Library option
set to /MT (use multi-threaded static libraries, /MTd for debug). If
your project uses something else, for example /MD (use multi-threaded
DLLs, /MDd for debug), you need to change the setting in the Google
Test project to match your project's.
To update this setting open the project properties in the Visual
Studio IDE then select the branch Configuration Properties | C/C++ |
Code Generation and change the option "Runtime Library". You may also try
using gtest-md.vcproj instead of gtest.vcproj.
## I put my tests in a library and Google Test doesn't run them. What's happening? ##
Have you read a
[warning](V1_6_Primer.md#important-note-for-visual-c-users) on
the Google Test Primer page?
## I want to use Google Test with Visual Studio but don't know where to start. ##
Many people are in your position and one of the posted his solution to
our mailing list. Here is his link:
http://hassanjamilahmad.blogspot.com/2009/07/gtest-starters-help.html.
## I am seeing compile errors mentioning std::type\_traits when I try to use Google Test on Solaris. ##
Google Test uses parts of the standard C++ library that SunStudio does not support.
Our users reported success using alternative implementations. Try running the build after runing this commad:
`export CC=cc CXX=CC CXXFLAGS='-library=stlport4'`
## How can my code detect if it is running in a test? ##
If you write code that sniffs whether it's running in a test and does
different things accordingly, you are leaking test-only logic into
production code and there is no easy way to ensure that the test-only
code paths aren't run by mistake in production. Such cleverness also
leads to
[Heisenbugs](http://en.wikipedia.org/wiki/Unusual_software_bug#Heisenbug).
Therefore we strongly advise against the practice, and Google Test doesn't
provide a way to do it.
In general, the recommended way to cause the code to behave
differently under test is [dependency injection](http://jamesshore.com/Blog/Dependency-Injection-Demystified.html).
You can inject different functionality from the test and from the
production code. Since your production code doesn't link in the
for-test logic at all, there is no danger in accidentally running it.
However, if you _really_, _really_, _really_ have no choice, and if
you follow the rule of ending your test program names with `_test`,
you can use the _horrible_ hack of sniffing your executable name
(`argv[0]` in `main()`) to know whether the code is under test.
## Google Test defines a macro that clashes with one defined by another library. How do I deal with that? ##
In C++, macros don't obey namespaces. Therefore two libraries that
both define a macro of the same name will clash if you `#include` both
definitions. In case a Google Test macro clashes with another
library, you can force Google Test to rename its macro to avoid the
conflict.
Specifically, if both Google Test and some other code define macro
`FOO`, you can add
```
-DGTEST_DONT_DEFINE_FOO=1
```
to the compiler flags to tell Google Test to change the macro's name
from `FOO` to `GTEST_FOO`. For example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write
```
GTEST_TEST(SomeTest, DoesThis) { ... }
```
instead of
```
TEST(SomeTest, DoesThis) { ... }
```
in order to define a test.
Currently, the following `TEST`, `FAIL`, `SUCCEED`, and the basic comparison assertion macros can have alternative names. You can see the full list of covered macros [here](http://www.google.com/codesearch?q=if+!GTEST_DONT_DEFINE_\w%2B+package:http://googletest\.googlecode\.com+file:/include/gtest/gtest.h). More information can be found in the "Avoiding Macro Name Clashes" section of the README file.
## My question is not covered in your FAQ! ##
If you cannot find the answer to your question in this FAQ, there are
some other resources you can use:
1. read other [wiki pages](http://code.google.com/p/googletest/w/list),
1. search the mailing list [archive](http://groups.google.com/group/googletestframework/topics),
1. ask it on [googletestframework@googlegroups.com](mailto:googletestframework@googlegroups.com) and someone will answer it (to prevent spam, we require you to join the [discussion group](http://groups.google.com/group/googletestframework) before you can post.).
Please note that creating an issue in the
[issue tracker](http://code.google.com/p/googletest/issues/list) is _not_
a good way to get your answer, as it is monitored infrequently by a
very small number of people.
When asking a question, it's helpful to provide as much of the
following information as possible (people cannot help you if there's
not enough information in your question):
* the version (or the revision number if you check out from SVN directly) of Google Test you use (Google Test is under active development, so it's possible that your problem has been solved in a later version),
* your operating system,
* the name and version of your compiler,
* the complete command line flags you give to your compiler,
* the complete compiler error messages (if the question is about compilation),
* the _actual_ code (ideally, a minimal but complete program) that has the problem you encounter.
googletest/docs/V1_6_Primer.md deleted 100644 → 0
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# Introduction: Why Google C++ Testing Framework? #
_Google C++ Testing Framework_ helps you write better C++ tests.
No matter whether you work on Linux, Windows, or a Mac, if you write C++ code,
Google Test can help you.
So what makes a good test, and how does Google C++ Testing Framework fit in? We believe:
1. Tests should be _independent_ and _repeatable_. It's a pain to debug a test that succeeds or fails as a result of other tests. Google C++ Testing Framework isolates the tests by running each of them on a different object. When a test fails, Google C++ Testing Framework allows you to run it in isolation for quick debugging.
1. Tests should be well _organized_ and reflect the structure of the tested code. Google C++ Testing Framework groups related tests into test cases that can share data and subroutines. This common pattern is easy to recognize and makes tests easy to maintain. Such consistency is especially helpful when people switch projects and start to work on a new code base.
1. Tests should be _portable_ and _reusable_. The open-source community has a lot of code that is platform-neutral, its tests should also be platform-neutral. Google C++ Testing Framework works on different OSes, with different compilers (gcc, MSVC, and others), with or without exceptions, so Google C++ Testing Framework tests can easily work with a variety of configurations. (Note that the current release only contains build scripts for Linux - we are actively working on scripts for other platforms.)
1. When tests fail, they should provide as much _information_ about the problem as possible. Google C++ Testing Framework doesn't stop at the first test failure. Instead, it only stops the current test and continues with the next. You can also set up tests that report non-fatal failures after which the current test continues. Thus, you can detect and fix multiple bugs in a single run-edit-compile cycle.
1. The testing framework should liberate test writers from housekeeping chores and let them focus on the test _content_. Google C++ Testing Framework automatically keeps track of all tests defined, and doesn't require the user to enumerate them in order to run them.
1. Tests should be _fast_. With Google C++ Testing Framework, you can reuse shared resources across tests and pay for the set-up/tear-down only once, without making tests depend on each other.
Since Google C++ Testing Framework is based on the popular xUnit
architecture, you'll feel right at home if you've used JUnit or PyUnit before.
If not, it will take you about 10 minutes to learn the basics and get started.
So let's go!
_Note:_ We sometimes refer to Google C++ Testing Framework informally
as _Google Test_.
# Setting up a New Test Project #
To write a test program using Google Test, you need to compile Google
Test into a library and link your test with it. We provide build
files for some popular build systems: `msvc/` for Visual Studio,
`xcode/` for Mac Xcode, `make/` for GNU make, `codegear/` for Borland
C++ Builder, and the autotools script (deprecated) and
`CMakeLists.txt` for CMake (recommended) in the Google Test root
directory. If your build system is not on this list, you can take a
look at `make/Makefile` to learn how Google Test should be compiled
(basically you want to compile `src/gtest-all.cc` with `GTEST_ROOT`
and `GTEST_ROOT/include` in the header search path, where `GTEST_ROOT`
is the Google Test root directory).
Once you are able to compile the Google Test library, you should
create a project or build target for your test program. Make sure you
have `GTEST_ROOT/include` in the header search path so that the
compiler can find `"gtest/gtest.h"` when compiling your test. Set up
your test project to link with the Google Test library (for example,
in Visual Studio, this is done by adding a dependency on
`gtest.vcproj`).
If you still have questions, take a look at how Google Test's own
tests are built and use them as examples.
# Basic Concepts #
When using Google Test, you start by writing _assertions_, which are statements
that check whether a condition is true. An assertion's result can be _success_,
_nonfatal failure_, or _fatal failure_. If a fatal failure occurs, it aborts
the current function; otherwise the program continues normally.
_Tests_ use assertions to verify the tested code's behavior. If a test crashes
or has a failed assertion, then it _fails_; otherwise it _succeeds_.
A _test case_ contains one or many tests. You should group your tests into test
cases that reflect the structure of the tested code. When multiple tests in a
test case need to share common objects and subroutines, you can put them into a
_test fixture_ class.
A _test program_ can contain multiple test cases.
We'll now explain how to write a test program, starting at the individual
assertion level and building up to tests and test cases.
# Assertions #
Google Test assertions are macros that resemble function calls. You test a
class or function by making assertions about its behavior. When an assertion
fails, Google Test prints the assertion's source file and line number location,
along with a failure message. You may also supply a custom failure message
which will be appended to Google Test's message.
The assertions come in pairs that test the same thing but have different
effects on the current function. `ASSERT_*` versions generate fatal failures
when they fail, and **abort the current function**. `EXPECT_*` versions generate
nonfatal failures, which don't abort the current function. Usually `EXPECT_*`
are preferred, as they allow more than one failures to be reported in a test.
However, you should use `ASSERT_*` if it doesn't make sense to continue when
the assertion in question fails.
Since a failed `ASSERT_*` returns from the current function immediately,
possibly skipping clean-up code that comes after it, it may cause a space leak.
Depending on the nature of the leak, it may or may not be worth fixing - so
keep this in mind if you get a heap checker error in addition to assertion
errors.
To provide a custom failure message, simply stream it into the macro using the
`<<` operator, or a sequence of such operators. An example:
```
ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
for (int i = 0; i < x.size(); ++i) {
EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
}
```
Anything that can be streamed to an `ostream` can be streamed to an assertion
macro--in particular, C strings and `string` objects. If a wide string
(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
streamed to an assertion, it will be translated to UTF-8 when printed.
## Basic Assertions ##
These assertions do basic true/false condition testing.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_TRUE(`_condition_`)`; | `EXPECT_TRUE(`_condition_`)`; | _condition_ is true |
| `ASSERT_FALSE(`_condition_`)`; | `EXPECT_FALSE(`_condition_`)`; | _condition_ is false |
Remember, when they fail, `ASSERT_*` yields a fatal failure and
returns from the current function, while `EXPECT_*` yields a nonfatal
failure, allowing the function to continue running. In either case, an
assertion failure means its containing test fails.
_Availability_: Linux, Windows, Mac.
## Binary Comparison ##
This section describes assertions that compare two values.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
|`ASSERT_EQ(`_expected_`, `_actual_`);`|`EXPECT_EQ(`_expected_`, `_actual_`);`| _expected_ `==` _actual_ |
|`ASSERT_NE(`_val1_`, `_val2_`);` |`EXPECT_NE(`_val1_`, `_val2_`);` | _val1_ `!=` _val2_ |
|`ASSERT_LT(`_val1_`, `_val2_`);` |`EXPECT_LT(`_val1_`, `_val2_`);` | _val1_ `<` _val2_ |
|`ASSERT_LE(`_val1_`, `_val2_`);` |`EXPECT_LE(`_val1_`, `_val2_`);` | _val1_ `<=` _val2_ |
|`ASSERT_GT(`_val1_`, `_val2_`);` |`EXPECT_GT(`_val1_`, `_val2_`);` | _val1_ `>` _val2_ |
|`ASSERT_GE(`_val1_`, `_val2_`);` |`EXPECT_GE(`_val1_`, `_val2_`);` | _val1_ `>=` _val2_ |
In the event of a failure, Google Test prints both _val1_ and _val2_
. In `ASSERT_EQ*` and `EXPECT_EQ*` (and all other equality assertions
we'll introduce later), you should put the expression you want to test
in the position of _actual_, and put its expected value in _expected_,
as Google Test's failure messages are optimized for this convention.
Value arguments must be comparable by the assertion's comparison
operator or you'll get a compiler error. We used to require the
arguments to support the `<<` operator for streaming to an `ostream`,
but it's no longer necessary since v1.6.0 (if `<<` is supported, it
will be called to print the arguments when the assertion fails;
otherwise Google Test will attempt to print them in the best way it
can. For more details and how to customize the printing of the
arguments, see this Google Mock [recipe](../../googlemock/docs/CookBook.md#teaching-google-mock-how-to-print-your-values).).
These assertions can work with a user-defined type, but only if you define the
corresponding comparison operator (e.g. `==`, `<`, etc). If the corresponding
operator is defined, prefer using the `ASSERT_*()` macros because they will
print out not only the result of the comparison, but the two operands as well.
Arguments are always evaluated exactly once. Therefore, it's OK for the
arguments to have side effects. However, as with any ordinary C/C++ function,
the arguments' evaluation order is undefined (i.e. the compiler is free to
choose any order) and your code should not depend on any particular argument
evaluation order.
`ASSERT_EQ()` does pointer equality on pointers. If used on two C strings, it
tests if they are in the same memory location, not if they have the same value.
Therefore, if you want to compare C strings (e.g. `const char*`) by value, use
`ASSERT_STREQ()` , which will be described later on. In particular, to assert
that a C string is `NULL`, use `ASSERT_STREQ(NULL, c_string)` . However, to
compare two `string` objects, you should use `ASSERT_EQ`.
Macros in this section work with both narrow and wide string objects (`string`
and `wstring`).
_Availability_: Linux, Windows, Mac.
## String Comparison ##
The assertions in this group compare two **C strings**. If you want to compare
two `string` objects, use `EXPECT_EQ`, `EXPECT_NE`, and etc instead.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_STREQ(`_expected\_str_`, `_actual\_str_`);` | `EXPECT_STREQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content |
| `ASSERT_STRNE(`_str1_`, `_str2_`);` | `EXPECT_STRNE(`_str1_`, `_str2_`);` | the two C strings have different content |
| `ASSERT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);`| `EXPECT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content, ignoring case |
| `ASSERT_STRCASENE(`_str1_`, `_str2_`);`| `EXPECT_STRCASENE(`_str1_`, `_str2_`);` | the two C strings have different content, ignoring case |
Note that "CASE" in an assertion name means that case is ignored.
`*STREQ*` and `*STRNE*` also accept wide C strings (`wchar_t*`). If a
comparison of two wide strings fails, their values will be printed as UTF-8
narrow strings.
A `NULL` pointer and an empty string are considered _different_.
_Availability_: Linux, Windows, Mac.
See also: For more string comparison tricks (substring, prefix, suffix, and
regular expression matching, for example), see the [Advanced Google Test Guide](V1_6_AdvancedGuide.md).
# Simple Tests #
To create a test:
1. Use the `TEST()` macro to define and name a test function, These are ordinary C++ functions that don't return a value.
1. In this function, along with any valid C++ statements you want to include, use the various Google Test assertions to check values.
1. The test's result is determined by the assertions; if any assertion in the test fails (either fatally or non-fatally), or if the test crashes, the entire test fails. Otherwise, it succeeds.
```
TEST(test_case_name, test_name) {
... test body ...
}
```
`TEST()` arguments go from general to specific. The _first_ argument is the
name of the test case, and the _second_ argument is the test's name within the
test case. Both names must be valid C++ identifiers, and they should not contain underscore (`_`). A test's _full name_ consists of its containing test case and its
individual name. Tests from different test cases can have the same individual
name.
For example, let's take a simple integer function:
```
int Factorial(int n); // Returns the factorial of n
```
A test case for this function might look like:
```
// Tests factorial of 0.
TEST(FactorialTest, HandlesZeroInput) {
EXPECT_EQ(1, Factorial(0));
}
// Tests factorial of positive numbers.
TEST(FactorialTest, HandlesPositiveInput) {
EXPECT_EQ(1, Factorial(1));
EXPECT_EQ(2, Factorial(2));
EXPECT_EQ(6, Factorial(3));
EXPECT_EQ(40320, Factorial(8));
}
```
Google Test groups the test results by test cases, so logically-related tests
should be in the same test case; in other words, the first argument to their
`TEST()` should be the same. In the above example, we have two tests,
`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
case `FactorialTest`.
_Availability_: Linux, Windows, Mac.
# Test Fixtures: Using the Same Data Configuration for Multiple Tests #
If you find yourself writing two or more tests that operate on similar data,
you can use a _test fixture_. It allows you to reuse the same configuration of
objects for several different tests.
To create a fixture, just:
1. Derive a class from `::testing::Test` . Start its body with `protected:` or `public:` as we'll want to access fixture members from sub-classes.
1. Inside the class, declare any objects you plan to use.
1. If necessary, write a default constructor or `SetUp()` function to prepare the objects for each test. A common mistake is to spell `SetUp()` as `Setup()` with a small `u` - don't let that happen to you.
1. If necessary, write a destructor or `TearDown()` function to release any resources you allocated in `SetUp()` . To learn when you should use the constructor/destructor and when you should use `SetUp()/TearDown()`, read this [FAQ entry](V1_6_FAQ.md#should-i-use-the-constructordestructor-of-the-test-fixture-or-the-set-uptear-down-function).
1. If needed, define subroutines for your tests to share.
When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
access objects and subroutines in the test fixture:
```
TEST_F(test_case_name, test_name) {
... test body ...
}
```
Like `TEST()`, the first argument is the test case name, but for `TEST_F()`
this must be the name of the test fixture class. You've probably guessed: `_F`
is for fixture.
Unfortunately, the C++ macro system does not allow us to create a single macro
that can handle both types of tests. Using the wrong macro causes a compiler
error.
Also, you must first define a test fixture class before using it in a
`TEST_F()`, or you'll get the compiler error "`virtual outside class
declaration`".
For each test defined with `TEST_F()`, Google Test will:
1. Create a _fresh_ test fixture at runtime
1. Immediately initialize it via `SetUp()` ,
1. Run the test
1. Clean up by calling `TearDown()`
1. Delete the test fixture. Note that different tests in the same test case have different test fixture objects, and Google Test always deletes a test fixture before it creates the next one. Google Test does not reuse the same test fixture for multiple tests. Any changes one test makes to the fixture do not affect other tests.
As an example, let's write tests for a FIFO queue class named `Queue`, which
has the following interface:
```
template <typename E> // E is the element type.
class Queue {
public:
Queue();
void Enqueue(const E& element);
E* Dequeue(); // Returns NULL if the queue is empty.
size_t size() const;
...
};
```
First, define a fixture class. By convention, you should give it the name
`FooTest` where `Foo` is the class being tested.
```
class QueueTest : public ::testing::Test {
protected:
virtual void SetUp() {
q1_.Enqueue(1);
q2_.Enqueue(2);
q2_.Enqueue(3);
}
// virtual void TearDown() {}
Queue<int> q0_;
Queue<int> q1_;
Queue<int> q2_;
};
```
In this case, `TearDown()` is not needed since we don't have to clean up after
each test, other than what's already done by the destructor.
Now we'll write tests using `TEST_F()` and this fixture.
```
TEST_F(QueueTest, IsEmptyInitially) {
EXPECT_EQ(0, q0_.size());
}
TEST_F(QueueTest, DequeueWorks) {
int* n = q0_.Dequeue();
EXPECT_EQ(NULL, n);
n = q1_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(1, *n);
EXPECT_EQ(0, q1_.size());
delete n;
n = q2_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(2, *n);
EXPECT_EQ(1, q2_.size());
delete n;
}
```
The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
to use `EXPECT_*` when you want the test to continue to reveal more errors
after the assertion failure, and use `ASSERT_*` when continuing after failure
doesn't make sense. For example, the second assertion in the `Dequeue` test is
`ASSERT_TRUE(n != NULL)`, as we need to dereference the pointer `n` later,
which would lead to a segfault when `n` is `NULL`.
When these tests run, the following happens:
1. Google Test constructs a `QueueTest` object (let's call it `t1` ).
1. `t1.SetUp()` initializes `t1` .
1. The first test ( `IsEmptyInitially` ) runs on `t1` .
1. `t1.TearDown()` cleans up after the test finishes.
1. `t1` is destructed.
1. The above steps are repeated on another `QueueTest` object, this time running the `DequeueWorks` test.
_Availability_: Linux, Windows, Mac.
_Note_: Google Test automatically saves all _Google Test_ flags when a test
object is constructed, and restores them when it is destructed.
# Invoking the Tests #
`TEST()` and `TEST_F()` implicitly register their tests with Google Test. So, unlike with many other C++ testing frameworks, you don't have to re-list all your defined tests in order to run them.
After defining your tests, you can run them with `RUN_ALL_TESTS()` , which returns `0` if all the tests are successful, or `1` otherwise. Note that `RUN_ALL_TESTS()` runs _all tests_ in your link unit -- they can be from different test cases, or even different source files.
When invoked, the `RUN_ALL_TESTS()` macro:
1. Saves the state of all Google Test flags.
1. Creates a test fixture object for the first test.
1. Initializes it via `SetUp()`.
1. Runs the test on the fixture object.
1. Cleans up the fixture via `TearDown()`.
1. Deletes the fixture.
1. Restores the state of all Google Test flags.
1. Repeats the above steps for the next test, until all tests have run.
In addition, if the text fixture's constructor generates a fatal failure in
step 2, there is no point for step 3 - 5 and they are thus skipped. Similarly,
if step 3 generates a fatal failure, step 4 will be skipped.
_Important_: You must not ignore the return value of `RUN_ALL_TESTS()`, or `gcc`
will give you a compiler error. The rationale for this design is that the
automated testing service determines whether a test has passed based on its
exit code, not on its stdout/stderr output; thus your `main()` function must
return the value of `RUN_ALL_TESTS()`.
Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than once
conflicts with some advanced Google Test features (e.g. thread-safe death
tests) and thus is not supported.
_Availability_: Linux, Windows, Mac.
# Writing the main() Function #
You can start from this boilerplate:
```
#include "this/package/foo.h"
#include "gtest/gtest.h"
namespace {
// The fixture for testing class Foo.
class FooTest : public ::testing::Test {
protected:
// You can remove any or all of the following functions if its body
// is empty.
FooTest() {
// You can do set-up work for each test here.
}
virtual ~FooTest() {
// You can do clean-up work that doesn't throw exceptions here.
}
// If the constructor and destructor are not enough for setting up
// and cleaning up each test, you can define the following methods:
virtual void SetUp() {
// Code here will be called immediately after the constructor (right
// before each test).
}
virtual void TearDown() {
// Code here will be called immediately after each test (right
// before the destructor).
}
// Objects declared here can be used by all tests in the test case for Foo.
};
// Tests that the Foo::Bar() method does Abc.
TEST_F(FooTest, MethodBarDoesAbc) {
const string input_filepath = "this/package/testdata/myinputfile.dat";
const string output_filepath = "this/package/testdata/myoutputfile.dat";
Foo f;
EXPECT_EQ(0, f.Bar(input_filepath, output_filepath));
}
// Tests that Foo does Xyz.
TEST_F(FooTest, DoesXyz) {
// Exercises the Xyz feature of Foo.
}
} // namespace
int main(int argc, char **argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
The `::testing::InitGoogleTest()` function parses the command line for Google
Test flags, and removes all recognized flags. This allows the user to control a
test program's behavior via various flags, which we'll cover in [AdvancedGuide](V1_6_AdvancedGuide.md).
You must call this function before calling `RUN_ALL_TESTS()`, or the flags
won't be properly initialized.
On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
in programs compiled in `UNICODE` mode as well.
But maybe you think that writing all those main() functions is too much work? We agree with you completely and that's why Google Test provides a basic implementation of main(). If it fits your needs, then just link your test with gtest\_main library and you are good to go.
## Important note for Visual C++ users ##
If you put your tests into a library and your `main()` function is in a different library or in your .exe file, those tests will not run. The reason is a [bug](https://connect.microsoft.com/feedback/viewfeedback.aspx?FeedbackID=244410&siteid=210) in Visual C++. When you define your tests, Google Test creates certain static objects to register them. These objects are not referenced from elsewhere but their constructors are still supposed to run. When Visual C++ linker sees that nothing in the library is referenced from other places it throws the library out. You have to reference your library with tests from your main program to keep the linker from discarding it. Here is how to do it. Somewhere in your library code declare a function:
```
__declspec(dllexport) int PullInMyLibrary() { return 0; }
```
If you put your tests in a static library (not DLL) then `__declspec(dllexport)` is not required. Now, in your main program, write a code that invokes that function:
```
int PullInMyLibrary();
static int dummy = PullInMyLibrary();
```
This will keep your tests referenced and will make them register themselves at startup.
In addition, if you define your tests in a static library, add `/OPT:NOREF` to your main program linker options. If you use MSVC++ IDE, go to your .exe project properties/Configuration Properties/Linker/Optimization and set References setting to `Keep Unreferenced Data (/OPT:NOREF)`. This will keep Visual C++ linker from discarding individual symbols generated by your tests from the final executable.
There is one more pitfall, though. If you use Google Test as a static library (that's how it is defined in gtest.vcproj) your tests must also reside in a static library. If you have to have them in a DLL, you _must_ change Google Test to build into a DLL as well. Otherwise your tests will not run correctly or will not run at all. The general conclusion here is: make your life easier - do not write your tests in libraries!
# Where to Go from Here #
Congratulations! You've learned the Google Test basics. You can start writing
and running Google Test tests, read some [samples](V1_6_Samples.md), or continue with
[AdvancedGuide](V1_6_AdvancedGuide.md), which describes many more useful Google Test features.
# Known Limitations #
Google Test is designed to be thread-safe. The implementation is
thread-safe on systems where the `pthreads` library is available. It
is currently _unsafe_ to use Google Test assertions from two threads
concurrently on other systems (e.g. Windows). In most tests this is
not an issue as usually the assertions are done in the main thread. If
you want to help, you can volunteer to implement the necessary
synchronization primitives in `gtest-port.h` for your platform.
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<b>P</b>ump is <b>U</b>seful for <b>M</b>eta <b>P</b>rogramming.
# The Problem #
Template and macro libraries often need to define many classes,
functions, or macros that vary only (or almost only) in the number of
arguments they take. It's a lot of repetitive, mechanical, and
error-prone work.
Variadic templates and variadic macros can alleviate the problem.
However, while both are being considered by the C++ committee, neither
is in the standard yet or widely supported by compilers. Thus they
are often not a good choice, especially when your code needs to be
portable. And their capabilities are still limited.
As a result, authors of such libraries often have to write scripts to
generate their implementation. However, our experience is that it's
tedious to write such scripts, which tend to reflect the structure of
the generated code poorly and are often hard to read and edit. For
example, a small change needed in the generated code may require some
non-intuitive, non-trivial changes in the script. This is especially
painful when experimenting with the code.
# Our Solution #
Pump (for Pump is Useful for Meta Programming, Pretty Useful for Meta
Programming, or Practical Utility for Meta Programming, whichever you
prefer) is a simple meta-programming tool for C++. The idea is that a
programmer writes a `foo.pump` file which contains C++ code plus meta
code that manipulates the C++ code. The meta code can handle
iterations over a range, nested iterations, local meta variable
definitions, simple arithmetic, and conditional expressions. You can
view it as a small Domain-Specific Language. The meta language is
designed to be non-intrusive (s.t. it won't confuse Emacs' C++ mode,
for example) and concise, making Pump code intuitive and easy to
maintain.
## Highlights ##
* The implementation is in a single Python script and thus ultra portable: no build or installation is needed and it works cross platforms.
* Pump tries to be smart with respect to [Google's style guide](http://code.google.com/p/google-styleguide/): it breaks long lines (easy to have when they are generated) at acceptable places to fit within 80 columns and indent the continuation lines correctly.
* The format is human-readable and more concise than XML.
* The format works relatively well with Emacs' C++ mode.
## Examples ##
The following Pump code (where meta keywords start with `$`, `[[` and `]]` are meta brackets, and `$$` starts a meta comment that ends with the line):
```
$var n = 3 $$ Defines a meta variable n.
$range i 0..n $$ Declares the range of meta iterator i (inclusive).
$for i [[
$$ Meta loop.
// Foo$i does blah for $i-ary predicates.
$range j 1..i
template <size_t N $for j [[, typename A$j]]>
class Foo$i {
$if i == 0 [[
blah a;
]] $elif i <= 2 [[
blah b;
]] $else [[
blah c;
]]
};
]]
```
will be translated by the Pump compiler to:
```
// Foo0 does blah for 0-ary predicates.
template <size_t N>
class Foo0 {
blah a;
};
// Foo1 does blah for 1-ary predicates.
template <size_t N, typename A1>
class Foo1 {
blah b;
};
// Foo2 does blah for 2-ary predicates.
template <size_t N, typename A1, typename A2>
class Foo2 {
blah b;
};
// Foo3 does blah for 3-ary predicates.
template <size_t N, typename A1, typename A2, typename A3>
class Foo3 {
blah c;
};
```
In another example,
```
$range i 1..n
Func($for i + [[a$i]]);
$$ The text between i and [[ is the separator between iterations.
```
will generate one of the following lines (without the comments), depending on the value of `n`:
```
Func(); // If n is 0.
Func(a1); // If n is 1.
Func(a1 + a2); // If n is 2.
Func(a1 + a2 + a3); // If n is 3.
// And so on...
```
## Constructs ##
We support the following meta programming constructs:
| `$var id = exp` | Defines a named constant value. `$id` is valid util the end of the current meta lexical block. |
|:----------------|:-----------------------------------------------------------------------------------------------|
| `$range id exp..exp` | Sets the range of an iteration variable, which can be reused in multiple loops later. |
| `$for id sep [[ code ]]` | Iteration. The range of `id` must have been defined earlier. `$id` is valid in `code`. |
| `$($)` | Generates a single `$` character. |
| `$id` | Value of the named constant or iteration variable. |
| `$(exp)` | Value of the expression. |
| `$if exp [[ code ]] else_branch` | Conditional. |
| `[[ code ]]` | Meta lexical block. |
| `cpp_code` | Raw C++ code. |
| `$$ comment` | Meta comment. |
**Note:** To give the user some freedom in formatting the Pump source
code, Pump ignores a new-line character if it's right after `$for foo`
or next to `[[` or `]]`. Without this rule you'll often be forced to write
very long lines to get the desired output. Therefore sometimes you may
need to insert an extra new-line in such places for a new-line to show
up in your output.
## Grammar ##
```
code ::= atomic_code*
atomic_code ::= $var id = exp
| $var id = [[ code ]]
| $range id exp..exp
| $for id sep [[ code ]]
| $($)
| $id
| $(exp)
| $if exp [[ code ]] else_branch
| [[ code ]]
| cpp_code
sep ::= cpp_code | empty_string
else_branch ::= $else [[ code ]]
| $elif exp [[ code ]] else_branch
| empty_string
exp ::= simple_expression_in_Python_syntax
```
## Code ##
You can find the source code of Pump in [scripts/pump.py](../scripts/pump.py). It is still
very unpolished and lacks automated tests, although it has been
successfully used many times. If you find a chance to use it in your
project, please let us know what you think! We also welcome help on
improving Pump.
## Real Examples ##
You can find real-world applications of Pump in [Google Test](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgoogletest\.googlecode\.com) and [Google Mock](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgooglemock\.googlecode\.com). The source file `foo.h.pump` generates `foo.h`.
## Tips ##
* If a meta variable is followed by a letter or digit, you can separate them using `[[]]`, which inserts an empty string. For example `Foo$j[[]]Helper` generate `Foo1Helper` when `j` is 1.
* To avoid extra-long Pump source lines, you can break a line anywhere you want by inserting `[[]]` followed by a new line. Since any new-line character next to `[[` or `]]` is ignored, the generated code won't contain this new line.
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If you're like us, you'd like to look at some Google Test sample code. The
[samples folder](../samples) has a number of well-commented samples showing how to use a
variety of Google Test features.
* [Sample #1](../samples/sample1_unittest.cc) shows the basic steps of using Google Test to test C++ functions.
* [Sample #2](../samples/sample2_unittest.cc) shows a more complex unit test for a class with multiple member functions.
* [Sample #3](../samples/sample3_unittest.cc) uses a test fixture.
* [Sample #4](../samples/sample4_unittest.cc) is another basic example of using Google Test.
* [Sample #5](../samples/sample5_unittest.cc) teaches how to reuse a test fixture in multiple test cases by deriving sub-fixtures from it.
* [Sample #6](../samples/sample6_unittest.cc) demonstrates type-parameterized tests.
* [Sample #7](../samples/sample7_unittest.cc) teaches the basics of value-parameterized tests.
* [Sample #8](../samples/sample8_unittest.cc) shows using `Combine()` in value-parameterized tests.
* [Sample #9](../samples/sample9_unittest.cc) shows use of the listener API to modify Google Test's console output and the use of its reflection API to inspect test results.
* [Sample #10](../samples/sample10_unittest.cc) shows use of the listener API to implement a primitive memory leak checker.
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This guide will explain how to use the Google Testing Framework in your Xcode projects on Mac OS X. This tutorial begins by quickly explaining what to do for experienced users. After the quick start, the guide goes provides additional explanation about each step.
# Quick Start #
Here is the quick guide for using Google Test in your Xcode project.
1. Download the source from the [website](http://code.google.com/p/googletest) using this command: `svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only`
1. Open up the `gtest.xcodeproj` in the `googletest-read-only/xcode/` directory and build the gtest.framework.
1. Create a new "Shell Tool" target in your Xcode project called something like "UnitTests"
1. Add the gtest.framework to your project and add it to the "Link Binary with Libraries" build phase of "UnitTests"
1. Add your unit test source code to the "Compile Sources" build phase of "UnitTests"
1. Edit the "UnitTests" executable and add an environment variable named "DYLD\_FRAMEWORK\_PATH" with a value equal to the path to the framework containing the gtest.framework relative to the compiled executable.
1. Build and Go
The following sections further explain each of the steps listed above in depth, describing in more detail how to complete it including some variations.
# Get the Source #
Currently, the gtest.framework discussed here isn't available in a tagged release of Google Test, it is only available in the trunk. As explained at the Google Test [site](http://code.google.com/p/googletest/source/checkout">svn), you can get the code from anonymous SVN with this command:
```
svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only
```
Alternatively, if you are working with Subversion in your own code base, you can add Google Test as an external dependency to your own Subversion repository. By following this approach, everyone that checks out your svn repository will also receive a copy of Google Test (a specific version, if you wish) without having to check it out explicitly. This makes the set up of your project simpler and reduces the copied code in the repository.
To use `svn:externals`, decide where you would like to have the external source reside. You might choose to put the external source inside the trunk, because you want it to be part of the branch when you make a release. However, keeping it outside the trunk in a version-tagged directory called something like `third-party/googletest/1.0.1`, is another option. Once the location is established, use `svn propedit svn:externals _directory_` to set the svn:externals property on a directory in your repository. This directory won't contain the code, but be its versioned parent directory.
The command `svn propedit` will bring up your Subversion editor, making editing the long, (potentially multi-line) property simpler. This same method can be used to check out a tagged branch, by using the appropriate URL (e.g. `http://googletest.googlecode.com/svn/tags/release-1.0.1`). Additionally, the svn:externals property allows the specification of a particular revision of the trunk with the `-r_##_` option (e.g. `externals/src/googletest -r60 http://googletest.googlecode.com/svn/trunk`).
Here is an example of using the svn:externals properties on a trunk (read via `svn propget`) of a project. This value checks out a copy of Google Test into the `trunk/externals/src/googletest/` directory.
```
[Computer:svn] user$ svn propget svn:externals trunk
externals/src/googletest http://googletest.googlecode.com/svn/trunk
```
# Add the Framework to Your Project #
The next step is to build and add the gtest.framework to your own project. This guide describes two common ways below.
* **Option 1** --- The simplest way to add Google Test to your own project, is to open gtest.xcodeproj (found in the xcode/ directory of the Google Test trunk) and build the framework manually. Then, add the built framework into your project using the "Add->Existing Framework..." from the context menu or "Project->Add..." from the main menu. The gtest.framework is relocatable and contains the headers and object code that you'll need to make tests. This method requires rebuilding every time you upgrade Google Test in your project.
* **Option 2** --- If you are going to be living off the trunk of Google Test, incorporating its latest features into your unit tests (or are a Google Test developer yourself). You'll want to rebuild the framework every time the source updates. to do this, you'll need to add the gtest.xcodeproj file, not the framework itself, to your own Xcode project. Then, from the build products that are revealed by the project's disclosure triangle, you can find the gtest.framework, which can be added to your targets (discussed below).
# Make a Test Target #
To start writing tests, make a new "Shell Tool" target. This target template is available under BSD, Cocoa, or Carbon. Add your unit test source code to the "Compile Sources" build phase of the target.
Next, you'll want to add gtest.framework in two different ways, depending upon which option you chose above.
* **Option 1** --- During compilation, Xcode will need to know that you are linking against the gtest.framework. Add the gtest.framework to the "Link Binary with Libraries" build phase of your test target. This will include the Google Test headers in your header search path, and will tell the linker where to find the library.
* **Option 2** --- If your working out of the trunk, you'll also want to add gtest.framework to your "Link Binary with Libraries" build phase of your test target. In addition, you'll want to add the gtest.framework as a dependency to your unit test target. This way, Xcode will make sure that gtest.framework is up to date, every time your build your target. Finally, if you don't share build directories with Google Test, you'll have to copy the gtest.framework into your own build products directory using a "Run Script" build phase.
# Set Up the Executable Run Environment #
Since the unit test executable is a shell tool, it doesn't have a bundle with a `Contents/Frameworks` directory, in which to place gtest.framework. Instead, the dynamic linker must be told at runtime to search for the framework in another location. This can be accomplished by setting the "DYLD\_FRAMEWORK\_PATH" environment variable in the "Edit Active Executable ..." Arguments tab, under "Variables to be set in the environment:". The path for this value is the path (relative or absolute) of the directory containing the gtest.framework.
If you haven't set up the DYLD\_FRAMEWORK\_PATH, correctly, you might get a message like this:
```
[Session started at 2008-08-15 06:23:57 -0600.]
dyld: Library not loaded: @loader_path/../Frameworks/gtest.framework/Versions/A/gtest
Referenced from: /Users/username/Documents/Sandbox/gtestSample/build/Debug/WidgetFrameworkTest
Reason: image not found
```
To correct this problem, got to the directory containing the executable named in "Referenced from:" value in the error message above. Then, with the terminal in this location, find the relative path to the directory containing the gtest.framework. That is the value you'll need to set as the DYLD\_FRAMEWORK\_PATH.
# Build and Go #
Now, when you click "Build and Go", the test will be executed. Dumping out something like this:
```
[Session started at 2008-08-06 06:36:13 -0600.]
[==========] Running 2 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 2 tests from WidgetInitializerTest
[ RUN ] WidgetInitializerTest.TestConstructor
[ OK ] WidgetInitializerTest.TestConstructor
[ RUN ] WidgetInitializerTest.TestConversion
[ OK ] WidgetInitializerTest.TestConversion
[----------] Global test environment tear-down
[==========] 2 tests from 1 test case ran.
[ PASSED ] 2 tests.
The Debugger has exited with status 0.
```
# Summary #
Unit testing is a valuable way to ensure your data model stays valid even during rapid development or refactoring. The Google Testing Framework is a great unit testing framework for C and C++ which integrates well with an Xcode development environment.
\ No newline at end of file
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Now that you have read [Primer](V1_7_Primer.md) and learned how to write tests
using Google Test, it's time to learn some new tricks. This document
will show you more assertions as well as how to construct complex
failure messages, propagate fatal failures, reuse and speed up your
test fixtures, and use various flags with your tests.
# More Assertions #
This section covers some less frequently used, but still significant,
assertions.
## Explicit Success and Failure ##
These three assertions do not actually test a value or expression. Instead,
they generate a success or failure directly. Like the macros that actually
perform a test, you may stream a custom failure message into the them.
| `SUCCEED();` |
|:-------------|
Generates a success. This does NOT make the overall test succeed. A test is
considered successful only if none of its assertions fail during its execution.
Note: `SUCCEED()` is purely documentary and currently doesn't generate any
user-visible output. However, we may add `SUCCEED()` messages to Google Test's
output in the future.
| `FAIL();` | `ADD_FAILURE();` | `ADD_FAILURE_AT("`_file\_path_`", `_line\_number_`);` |
|:-----------|:-----------------|:------------------------------------------------------|
`FAIL()` generates a fatal failure, while `ADD_FAILURE()` and `ADD_FAILURE_AT()` generate a nonfatal
failure. These are useful when control flow, rather than a Boolean expression,
deteremines the test's success or failure. For example, you might want to write
something like:
```
switch(expression) {
case 1: ... some checks ...
case 2: ... some other checks
...
default: FAIL() << "We shouldn't get here.";
}
```
_Availability_: Linux, Windows, Mac.
## Exception Assertions ##
These are for verifying that a piece of code throws (or does not
throw) an exception of the given type:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_THROW(`_statement_, _exception\_type_`);` | `EXPECT_THROW(`_statement_, _exception\_type_`);` | _statement_ throws an exception of the given type |
| `ASSERT_ANY_THROW(`_statement_`);` | `EXPECT_ANY_THROW(`_statement_`);` | _statement_ throws an exception of any type |
| `ASSERT_NO_THROW(`_statement_`);` | `EXPECT_NO_THROW(`_statement_`);` | _statement_ doesn't throw any exception |
Examples:
```
ASSERT_THROW(Foo(5), bar_exception);
EXPECT_NO_THROW({
int n = 5;
Bar(&n);
});
```
_Availability_: Linux, Windows, Mac; since version 1.1.0.
## Predicate Assertions for Better Error Messages ##
Even though Google Test has a rich set of assertions, they can never be
complete, as it's impossible (nor a good idea) to anticipate all the scenarios
a user might run into. Therefore, sometimes a user has to use `EXPECT_TRUE()`
to check a complex expression, for lack of a better macro. This has the problem
of not showing you the values of the parts of the expression, making it hard to
understand what went wrong. As a workaround, some users choose to construct the
failure message by themselves, streaming it into `EXPECT_TRUE()`. However, this
is awkward especially when the expression has side-effects or is expensive to
evaluate.
Google Test gives you three different options to solve this problem:
### Using an Existing Boolean Function ###
If you already have a function or a functor that returns `bool` (or a type
that can be implicitly converted to `bool`), you can use it in a _predicate
assertion_ to get the function arguments printed for free:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_PRED1(`_pred1, val1_`);` | `EXPECT_PRED1(`_pred1, val1_`);` | _pred1(val1)_ returns true |
| `ASSERT_PRED2(`_pred2, val1, val2_`);` | `EXPECT_PRED2(`_pred2, val1, val2_`);` | _pred2(val1, val2)_ returns true |
| ... | ... | ... |
In the above, _predn_ is an _n_-ary predicate function or functor, where
_val1_, _val2_, ..., and _valn_ are its arguments. The assertion succeeds
if the predicate returns `true` when applied to the given arguments, and fails
otherwise. When the assertion fails, it prints the value of each argument. In
either case, the arguments are evaluated exactly once.
Here's an example. Given
```
// Returns true iff m and n have no common divisors except 1.
bool MutuallyPrime(int m, int n) { ... }
const int a = 3;
const int b = 4;
const int c = 10;
```
the assertion `EXPECT_PRED2(MutuallyPrime, a, b);` will succeed, while the
assertion `EXPECT_PRED2(MutuallyPrime, b, c);` will fail with the message
<pre>
!MutuallyPrime(b, c) is false, where<br>
b is 4<br>
c is 10<br>
</pre>
**Notes:**
1. If you see a compiler error "no matching function to call" when using `ASSERT_PRED*` or `EXPECT_PRED*`, please see [this](V1_7_FAQ.md#the-compiler-complains-about-undefined-references-to-some-static-const-member-variables-but-i-did-define-them-in-the-class-body-whats-wrong) for how to resolve it.
1. Currently we only provide predicate assertions of arity <= 5. If you need a higher-arity assertion, let us know.
_Availability_: Linux, Windows, Mac
### Using a Function That Returns an AssertionResult ###
While `EXPECT_PRED*()` and friends are handy for a quick job, the
syntax is not satisfactory: you have to use different macros for
different arities, and it feels more like Lisp than C++. The
`::testing::AssertionResult` class solves this problem.
An `AssertionResult` object represents the result of an assertion
(whether it's a success or a failure, and an associated message). You
can create an `AssertionResult` using one of these factory
functions:
```
namespace testing {
// Returns an AssertionResult object to indicate that an assertion has
// succeeded.
AssertionResult AssertionSuccess();
// Returns an AssertionResult object to indicate that an assertion has
// failed.
AssertionResult AssertionFailure();
}
```
You can then use the `<<` operator to stream messages to the
`AssertionResult` object.
To provide more readable messages in Boolean assertions
(e.g. `EXPECT_TRUE()`), write a predicate function that returns
`AssertionResult` instead of `bool`. For example, if you define
`IsEven()` as:
```
::testing::AssertionResult IsEven(int n) {
if ((n % 2) == 0)
return ::testing::AssertionSuccess();
else
return ::testing::AssertionFailure() << n << " is odd";
}
```
instead of:
```
bool IsEven(int n) {
return (n % 2) == 0;
}
```
the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print:
<pre>
Value of: IsEven(Fib(4))<br>
Actual: false (*3 is odd*)<br>
Expected: true<br>
</pre>
instead of a more opaque
<pre>
Value of: IsEven(Fib(4))<br>
Actual: false<br>
Expected: true<br>
</pre>
If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE`
as well, and are fine with making the predicate slower in the success
case, you can supply a success message:
```
::testing::AssertionResult IsEven(int n) {
if ((n % 2) == 0)
return ::testing::AssertionSuccess() << n << " is even";
else
return ::testing::AssertionFailure() << n << " is odd";
}
```
Then the statement `EXPECT_FALSE(IsEven(Fib(6)))` will print
<pre>
Value of: IsEven(Fib(6))<br>
Actual: true (8 is even)<br>
Expected: false<br>
</pre>
_Availability_: Linux, Windows, Mac; since version 1.4.1.
### Using a Predicate-Formatter ###
If you find the default message generated by `(ASSERT|EXPECT)_PRED*` and
`(ASSERT|EXPECT)_(TRUE|FALSE)` unsatisfactory, or some arguments to your
predicate do not support streaming to `ostream`, you can instead use the
following _predicate-formatter assertions_ to _fully_ customize how the
message is formatted:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_PRED_FORMAT1(`_pred\_format1, val1_`);` | `EXPECT_PRED_FORMAT1(`_pred\_format1, val1_`); | _pred\_format1(val1)_ is successful |
| `ASSERT_PRED_FORMAT2(`_pred\_format2, val1, val2_`);` | `EXPECT_PRED_FORMAT2(`_pred\_format2, val1, val2_`);` | _pred\_format2(val1, val2)_ is successful |
| `...` | `...` | `...` |
The difference between this and the previous two groups of macros is that instead of
a predicate, `(ASSERT|EXPECT)_PRED_FORMAT*` take a _predicate-formatter_
(_pred\_formatn_), which is a function or functor with the signature:
`::testing::AssertionResult PredicateFormattern(const char* `_expr1_`, const char* `_expr2_`, ... const char* `_exprn_`, T1 `_val1_`, T2 `_val2_`, ... Tn `_valn_`);`
where _val1_, _val2_, ..., and _valn_ are the values of the predicate
arguments, and _expr1_, _expr2_, ..., and _exprn_ are the corresponding
expressions as they appear in the source code. The types `T1`, `T2`, ..., and
`Tn` can be either value types or reference types. For example, if an
argument has type `Foo`, you can declare it as either `Foo` or `const Foo&`,
whichever is appropriate.
A predicate-formatter returns a `::testing::AssertionResult` object to indicate
whether the assertion has succeeded or not. The only way to create such an
object is to call one of these factory functions:
As an example, let's improve the failure message in the previous example, which uses `EXPECT_PRED2()`:
```
// Returns the smallest prime common divisor of m and n,
// or 1 when m and n are mutually prime.
int SmallestPrimeCommonDivisor(int m, int n) { ... }
// A predicate-formatter for asserting that two integers are mutually prime.
::testing::AssertionResult AssertMutuallyPrime(const char* m_expr,
const char* n_expr,
int m,
int n) {
if (MutuallyPrime(m, n))
return ::testing::AssertionSuccess();
return ::testing::AssertionFailure()
<< m_expr << " and " << n_expr << " (" << m << " and " << n
<< ") are not mutually prime, " << "as they have a common divisor "
<< SmallestPrimeCommonDivisor(m, n);
}
```
With this predicate-formatter, we can use
```
EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);
```
to generate the message
<pre>
b and c (4 and 10) are not mutually prime, as they have a common divisor 2.<br>
</pre>
As you may have realized, many of the assertions we introduced earlier are
special cases of `(EXPECT|ASSERT)_PRED_FORMAT*`. In fact, most of them are
indeed defined using `(EXPECT|ASSERT)_PRED_FORMAT*`.
_Availability_: Linux, Windows, Mac.
## Floating-Point Comparison ##
Comparing floating-point numbers is tricky. Due to round-off errors, it is
very unlikely that two floating-points will match exactly. Therefore,
`ASSERT_EQ` 's naive comparison usually doesn't work. And since floating-points
can have a wide value range, no single fixed error bound works. It's better to
compare by a fixed relative error bound, except for values close to 0 due to
the loss of precision there.
In general, for floating-point comparison to make sense, the user needs to
carefully choose the error bound. If they don't want or care to, comparing in
terms of Units in the Last Place (ULPs) is a good default, and Google Test
provides assertions to do this. Full details about ULPs are quite long; if you
want to learn more, see
[this article on float comparison](http://www.cygnus-software.com/papers/comparingfloats/comparingfloats.htm).
### Floating-Point Macros ###
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_FLOAT_EQ(`_expected, actual_`);` | `EXPECT_FLOAT_EQ(`_expected, actual_`);` | the two `float` values are almost equal |
| `ASSERT_DOUBLE_EQ(`_expected, actual_`);` | `EXPECT_DOUBLE_EQ(`_expected, actual_`);` | the two `double` values are almost equal |
By "almost equal", we mean the two values are within 4 ULP's from each
other.
The following assertions allow you to choose the acceptable error bound:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_NEAR(`_val1, val2, abs\_error_`);` | `EXPECT_NEAR`_(val1, val2, abs\_error_`);` | the difference between _val1_ and _val2_ doesn't exceed the given absolute error |
_Availability_: Linux, Windows, Mac.
### Floating-Point Predicate-Format Functions ###
Some floating-point operations are useful, but not that often used. In order
to avoid an explosion of new macros, we provide them as predicate-format
functions that can be used in predicate assertion macros (e.g.
`EXPECT_PRED_FORMAT2`, etc).
```
EXPECT_PRED_FORMAT2(::testing::FloatLE, val1, val2);
EXPECT_PRED_FORMAT2(::testing::DoubleLE, val1, val2);
```
Verifies that _val1_ is less than, or almost equal to, _val2_. You can
replace `EXPECT_PRED_FORMAT2` in the above table with `ASSERT_PRED_FORMAT2`.
_Availability_: Linux, Windows, Mac.
## Windows HRESULT assertions ##
These assertions test for `HRESULT` success or failure.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_HRESULT_SUCCEEDED(`_expression_`);` | `EXPECT_HRESULT_SUCCEEDED(`_expression_`);` | _expression_ is a success `HRESULT` |
| `ASSERT_HRESULT_FAILED(`_expression_`);` | `EXPECT_HRESULT_FAILED(`_expression_`);` | _expression_ is a failure `HRESULT` |
The generated output contains the human-readable error message
associated with the `HRESULT` code returned by _expression_.
You might use them like this:
```
CComPtr shell;
ASSERT_HRESULT_SUCCEEDED(shell.CoCreateInstance(L"Shell.Application"));
CComVariant empty;
ASSERT_HRESULT_SUCCEEDED(shell->ShellExecute(CComBSTR(url), empty, empty, empty, empty));
```
_Availability_: Windows.
## Type Assertions ##
You can call the function
```
::testing::StaticAssertTypeEq<T1, T2>();
```
to assert that types `T1` and `T2` are the same. The function does
nothing if the assertion is satisfied. If the types are different,
the function call will fail to compile, and the compiler error message
will likely (depending on the compiler) show you the actual values of
`T1` and `T2`. This is mainly useful inside template code.
_Caveat:_ When used inside a member function of a class template or a
function template, `StaticAssertTypeEq<T1, T2>()` is effective _only if_
the function is instantiated. For example, given:
```
template <typename T> class Foo {
public:
void Bar() { ::testing::StaticAssertTypeEq<int, T>(); }
};
```
the code:
```
void Test1() { Foo<bool> foo; }
```
will _not_ generate a compiler error, as `Foo<bool>::Bar()` is never
actually instantiated. Instead, you need:
```
void Test2() { Foo<bool> foo; foo.Bar(); }
```
to cause a compiler error.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
## Assertion Placement ##
You can use assertions in any C++ function. In particular, it doesn't
have to be a method of the test fixture class. The one constraint is
that assertions that generate a fatal failure (`FAIL*` and `ASSERT_*`)
can only be used in void-returning functions. This is a consequence of
Google Test not using exceptions. By placing it in a non-void function
you'll get a confusing compile error like
`"error: void value not ignored as it ought to be"`.
If you need to use assertions in a function that returns non-void, one option
is to make the function return the value in an out parameter instead. For
example, you can rewrite `T2 Foo(T1 x)` to `void Foo(T1 x, T2* result)`. You
need to make sure that `*result` contains some sensible value even when the
function returns prematurely. As the function now returns `void`, you can use
any assertion inside of it.
If changing the function's type is not an option, you should just use
assertions that generate non-fatal failures, such as `ADD_FAILURE*` and
`EXPECT_*`.
_Note_: Constructors and destructors are not considered void-returning
functions, according to the C++ language specification, and so you may not use
fatal assertions in them. You'll get a compilation error if you try. A simple
workaround is to transfer the entire body of the constructor or destructor to a
private void-returning method. However, you should be aware that a fatal
assertion failure in a constructor does not terminate the current test, as your
intuition might suggest; it merely returns from the constructor early, possibly
leaving your object in a partially-constructed state. Likewise, a fatal
assertion failure in a destructor may leave your object in a
partially-destructed state. Use assertions carefully in these situations!
# Teaching Google Test How to Print Your Values #
When a test assertion such as `EXPECT_EQ` fails, Google Test prints the
argument values to help you debug. It does this using a
user-extensible value printer.
This printer knows how to print built-in C++ types, native arrays, STL
containers, and any type that supports the `<<` operator. For other
types, it prints the raw bytes in the value and hopes that you the
user can figure it out.
As mentioned earlier, the printer is _extensible_. That means
you can teach it to do a better job at printing your particular type
than to dump the bytes. To do that, define `<<` for your type:
```
#include <iostream>
namespace foo {
class Bar { ... }; // We want Google Test to be able to print instances of this.
// It's important that the << operator is defined in the SAME
// namespace that defines Bar. C++'s look-up rules rely on that.
::std::ostream& operator<<(::std::ostream& os, const Bar& bar) {
return os << bar.DebugString(); // whatever needed to print bar to os
}
} // namespace foo
```
Sometimes, this might not be an option: your team may consider it bad
style to have a `<<` operator for `Bar`, or `Bar` may already have a
`<<` operator that doesn't do what you want (and you cannot change
it). If so, you can instead define a `PrintTo()` function like this:
```
#include <iostream>
namespace foo {
class Bar { ... };
// It's important that PrintTo() is defined in the SAME
// namespace that defines Bar. C++'s look-up rules rely on that.
void PrintTo(const Bar& bar, ::std::ostream* os) {
*os << bar.DebugString(); // whatever needed to print bar to os
}
} // namespace foo
```
If you have defined both `<<` and `PrintTo()`, the latter will be used
when Google Test is concerned. This allows you to customize how the value
appears in Google Test's output without affecting code that relies on the
behavior of its `<<` operator.
If you want to print a value `x` using Google Test's value printer
yourself, just call `::testing::PrintToString(`_x_`)`, which
returns an `std::string`:
```
vector<pair<Bar, int> > bar_ints = GetBarIntVector();
EXPECT_TRUE(IsCorrectBarIntVector(bar_ints))
<< "bar_ints = " << ::testing::PrintToString(bar_ints);
```
# Death Tests #
In many applications, there are assertions that can cause application failure
if a condition is not met. These sanity checks, which ensure that the program
is in a known good state, are there to fail at the earliest possible time after
some program state is corrupted. If the assertion checks the wrong condition,
then the program may proceed in an erroneous state, which could lead to memory
corruption, security holes, or worse. Hence it is vitally important to test
that such assertion statements work as expected.
Since these precondition checks cause the processes to die, we call such tests
_death tests_. More generally, any test that checks that a program terminates
(except by throwing an exception) in an expected fashion is also a death test.
Note that if a piece of code throws an exception, we don't consider it "death"
for the purpose of death tests, as the caller of the code could catch the exception
and avoid the crash. If you want to verify exceptions thrown by your code,
see [Exception Assertions](#exception-assertions).
If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see [Catching Failures](#catching-failures).
## How to Write a Death Test ##
Google Test has the following macros to support death tests:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_DEATH(`_statement, regex_`); | `EXPECT_DEATH(`_statement, regex_`); | _statement_ crashes with the given error |
| `ASSERT_DEATH_IF_SUPPORTED(`_statement, regex_`); | `EXPECT_DEATH_IF_SUPPORTED(`_statement, regex_`); | if death tests are supported, verifies that _statement_ crashes with the given error; otherwise verifies nothing |
| `ASSERT_EXIT(`_statement, predicate, regex_`); | `EXPECT_EXIT(`_statement, predicate, regex_`); |_statement_ exits with the given error and its exit code matches _predicate_ |
where _statement_ is a statement that is expected to cause the process to
die, _predicate_ is a function or function object that evaluates an integer
exit status, and _regex_ is a regular expression that the stderr output of
_statement_ is expected to match. Note that _statement_ can be _any valid
statement_ (including _compound statement_) and doesn't have to be an
expression.
As usual, the `ASSERT` variants abort the current test function, while the
`EXPECT` variants do not.
**Note:** We use the word "crash" here to mean that the process
terminates with a _non-zero_ exit status code. There are two
possibilities: either the process has called `exit()` or `_exit()`
with a non-zero value, or it may be killed by a signal.
This means that if _statement_ terminates the process with a 0 exit
code, it is _not_ considered a crash by `EXPECT_DEATH`. Use
`EXPECT_EXIT` instead if this is the case, or if you want to restrict
the exit code more precisely.
A predicate here must accept an `int` and return a `bool`. The death test
succeeds only if the predicate returns `true`. Google Test defines a few
predicates that handle the most common cases:
```
::testing::ExitedWithCode(exit_code)
```
This expression is `true` if the program exited normally with the given exit
code.
```
::testing::KilledBySignal(signal_number) // Not available on Windows.
```
This expression is `true` if the program was killed by the given signal.
The `*_DEATH` macros are convenient wrappers for `*_EXIT` that use a predicate
that verifies the process' exit code is non-zero.
Note that a death test only cares about three things:
1. does _statement_ abort or exit the process?
1. (in the case of `ASSERT_EXIT` and `EXPECT_EXIT`) does the exit status satisfy _predicate_? Or (in the case of `ASSERT_DEATH` and `EXPECT_DEATH`) is the exit status non-zero? And
1. does the stderr output match _regex_?
In particular, if _statement_ generates an `ASSERT_*` or `EXPECT_*` failure, it will **not** cause the death test to fail, as Google Test assertions don't abort the process.
To write a death test, simply use one of the above macros inside your test
function. For example,
```
TEST(MyDeathTest, Foo) {
// This death test uses a compound statement.
ASSERT_DEATH({ int n = 5; Foo(&n); }, "Error on line .* of Foo()");
}
TEST(MyDeathTest, NormalExit) {
EXPECT_EXIT(NormalExit(), ::testing::ExitedWithCode(0), "Success");
}
TEST(MyDeathTest, KillMyself) {
EXPECT_EXIT(KillMyself(), ::testing::KilledBySignal(SIGKILL), "Sending myself unblockable signal");
}
```
verifies that:
* calling `Foo(5)` causes the process to die with the given error message,
* calling `NormalExit()` causes the process to print `"Success"` to stderr and exit with exit code 0, and
* calling `KillMyself()` kills the process with signal `SIGKILL`.
The test function body may contain other assertions and statements as well, if
necessary.
_Important:_ We strongly recommend you to follow the convention of naming your
test case (not test) `*DeathTest` when it contains a death test, as
demonstrated in the above example. The `Death Tests And Threads` section below
explains why.
If a test fixture class is shared by normal tests and death tests, you
can use typedef to introduce an alias for the fixture class and avoid
duplicating its code:
```
class FooTest : public ::testing::Test { ... };
typedef FooTest FooDeathTest;
TEST_F(FooTest, DoesThis) {
// normal test
}
TEST_F(FooDeathTest, DoesThat) {
// death test
}
```
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Cygwin, and Mac (the latter three are supported since v1.3.0). `(ASSERT|EXPECT)_DEATH_IF_SUPPORTED` are new in v1.4.0.
## Regular Expression Syntax ##
On POSIX systems (e.g. Linux, Cygwin, and Mac), Google Test uses the
[POSIX extended regular expression](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
syntax in death tests. To learn about this syntax, you may want to read this [Wikipedia entry](http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions).
On Windows, Google Test uses its own simple regular expression
implementation. It lacks many features you can find in POSIX extended
regular expressions. For example, we don't support union (`"x|y"`),
grouping (`"(xy)"`), brackets (`"[xy]"`), and repetition count
(`"x{5,7}"`), among others. Below is what we do support (Letter `A` denotes a
literal character, period (`.`), or a single `\\` escape sequence; `x`
and `y` denote regular expressions.):
| `c` | matches any literal character `c` |
|:----|:----------------------------------|
| `\\d` | matches any decimal digit |
| `\\D` | matches any character that's not a decimal digit |
| `\\f` | matches `\f` |
| `\\n` | matches `\n` |
| `\\r` | matches `\r` |
| `\\s` | matches any ASCII whitespace, including `\n` |
| `\\S` | matches any character that's not a whitespace |
| `\\t` | matches `\t` |
| `\\v` | matches `\v` |
| `\\w` | matches any letter, `_`, or decimal digit |
| `\\W` | matches any character that `\\w` doesn't match |
| `\\c` | matches any literal character `c`, which must be a punctuation |
| `\\.` | matches the `.` character |
| `.` | matches any single character except `\n` |
| `A?` | matches 0 or 1 occurrences of `A` |
| `A*` | matches 0 or many occurrences of `A` |
| `A+` | matches 1 or many occurrences of `A` |
| `^` | matches the beginning of a string (not that of each line) |
| `$` | matches the end of a string (not that of each line) |
| `xy` | matches `x` followed by `y` |
To help you determine which capability is available on your system,
Google Test defines macro `GTEST_USES_POSIX_RE=1` when it uses POSIX
extended regular expressions, or `GTEST_USES_SIMPLE_RE=1` when it uses
the simple version. If you want your death tests to work in both
cases, you can either `#if` on these macros or use the more limited
syntax only.
## How It Works ##
Under the hood, `ASSERT_EXIT()` spawns a new process and executes the
death test statement in that process. The details of how precisely
that happens depend on the platform and the variable
`::testing::GTEST_FLAG(death_test_style)` (which is initialized from the
command-line flag `--gtest_death_test_style`).
* On POSIX systems, `fork()` (or `clone()` on Linux) is used to spawn the child, after which:
* If the variable's value is `"fast"`, the death test statement is immediately executed.
* If the variable's value is `"threadsafe"`, the child process re-executes the unit test binary just as it was originally invoked, but with some extra flags to cause just the single death test under consideration to be run.
* On Windows, the child is spawned using the `CreateProcess()` API, and re-executes the binary to cause just the single death test under consideration to be run - much like the `threadsafe` mode on POSIX.
Other values for the variable are illegal and will cause the death test to
fail. Currently, the flag's default value is `"fast"`. However, we reserve the
right to change it in the future. Therefore, your tests should not depend on
this.
In either case, the parent process waits for the child process to complete, and checks that
1. the child's exit status satisfies the predicate, and
1. the child's stderr matches the regular expression.
If the death test statement runs to completion without dying, the child
process will nonetheless terminate, and the assertion fails.
## Death Tests And Threads ##
The reason for the two death test styles has to do with thread safety. Due to
well-known problems with forking in the presence of threads, death tests should
be run in a single-threaded context. Sometimes, however, it isn't feasible to
arrange that kind of environment. For example, statically-initialized modules
may start threads before main is ever reached. Once threads have been created,
it may be difficult or impossible to clean them up.
Google Test has three features intended to raise awareness of threading issues.
1. A warning is emitted if multiple threads are running when a death test is encountered.
1. Test cases with a name ending in "DeathTest" are run before all other tests.
1. It uses `clone()` instead of `fork()` to spawn the child process on Linux (`clone()` is not available on Cygwin and Mac), as `fork()` is more likely to cause the child to hang when the parent process has multiple threads.
It's perfectly fine to create threads inside a death test statement; they are
executed in a separate process and cannot affect the parent.
## Death Test Styles ##
The "threadsafe" death test style was introduced in order to help mitigate the
risks of testing in a possibly multithreaded environment. It trades increased
test execution time (potentially dramatically so) for improved thread safety.
We suggest using the faster, default "fast" style unless your test has specific
problems with it.
You can choose a particular style of death tests by setting the flag
programmatically:
```
::testing::FLAGS_gtest_death_test_style = "threadsafe";
```
You can do this in `main()` to set the style for all death tests in the
binary, or in individual tests. Recall that flags are saved before running each
test and restored afterwards, so you need not do that yourself. For example:
```
TEST(MyDeathTest, TestOne) {
::testing::FLAGS_gtest_death_test_style = "threadsafe";
// This test is run in the "threadsafe" style:
ASSERT_DEATH(ThisShouldDie(), "");
}
TEST(MyDeathTest, TestTwo) {
// This test is run in the "fast" style:
ASSERT_DEATH(ThisShouldDie(), "");
}
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
::testing::FLAGS_gtest_death_test_style = "fast";
return RUN_ALL_TESTS();
}
```
## Caveats ##
The _statement_ argument of `ASSERT_EXIT()` can be any valid C++ statement.
If it leaves the current function via a `return` statement or by throwing an exception,
the death test is considered to have failed. Some Google Test macros may return
from the current function (e.g. `ASSERT_TRUE()`), so be sure to avoid them in _statement_.
Since _statement_ runs in the child process, any in-memory side effect (e.g.
modifying a variable, releasing memory, etc) it causes will _not_ be observable
in the parent process. In particular, if you release memory in a death test,
your program will fail the heap check as the parent process will never see the
memory reclaimed. To solve this problem, you can
1. try not to free memory in a death test;
1. free the memory again in the parent process; or
1. do not use the heap checker in your program.
Due to an implementation detail, you cannot place multiple death test
assertions on the same line; otherwise, compilation will fail with an unobvious
error message.
Despite the improved thread safety afforded by the "threadsafe" style of death
test, thread problems such as deadlock are still possible in the presence of
handlers registered with `pthread_atfork(3)`.
# Using Assertions in Sub-routines #
## Adding Traces to Assertions ##
If a test sub-routine is called from several places, when an assertion
inside it fails, it can be hard to tell which invocation of the
sub-routine the failure is from. You can alleviate this problem using
extra logging or custom failure messages, but that usually clutters up
your tests. A better solution is to use the `SCOPED_TRACE` macro:
| `SCOPED_TRACE(`_message_`);` |
|:-----------------------------|
where _message_ can be anything streamable to `std::ostream`. This
macro will cause the current file name, line number, and the given
message to be added in every failure message. The effect will be
undone when the control leaves the current lexical scope.
For example,
```
10: void Sub1(int n) {
11: EXPECT_EQ(1, Bar(n));
12: EXPECT_EQ(2, Bar(n + 1));
13: }
14:
15: TEST(FooTest, Bar) {
16: {
17: SCOPED_TRACE("A"); // This trace point will be included in
18: // every failure in this scope.
19: Sub1(1);
20: }
21: // Now it won't.
22: Sub1(9);
23: }
```
could result in messages like these:
```
path/to/foo_test.cc:11: Failure
Value of: Bar(n)
Expected: 1
Actual: 2
Trace:
path/to/foo_test.cc:17: A
path/to/foo_test.cc:12: Failure
Value of: Bar(n + 1)
Expected: 2
Actual: 3
```
Without the trace, it would've been difficult to know which invocation
of `Sub1()` the two failures come from respectively. (You could add an
extra message to each assertion in `Sub1()` to indicate the value of
`n`, but that's tedious.)
Some tips on using `SCOPED_TRACE`:
1. With a suitable message, it's often enough to use `SCOPED_TRACE` at the beginning of a sub-routine, instead of at each call site.
1. When calling sub-routines inside a loop, make the loop iterator part of the message in `SCOPED_TRACE` such that you can know which iteration the failure is from.
1. Sometimes the line number of the trace point is enough for identifying the particular invocation of a sub-routine. In this case, you don't have to choose a unique message for `SCOPED_TRACE`. You can simply use `""`.
1. You can use `SCOPED_TRACE` in an inner scope when there is one in the outer scope. In this case, all active trace points will be included in the failure messages, in reverse order they are encountered.
1. The trace dump is clickable in Emacs' compilation buffer - hit return on a line number and you'll be taken to that line in the source file!
_Availability:_ Linux, Windows, Mac.
## Propagating Fatal Failures ##
A common pitfall when using `ASSERT_*` and `FAIL*` is not understanding that
when they fail they only abort the _current function_, not the entire test. For
example, the following test will segfault:
```
void Subroutine() {
// Generates a fatal failure and aborts the current function.
ASSERT_EQ(1, 2);
// The following won't be executed.
...
}
TEST(FooTest, Bar) {
Subroutine();
// The intended behavior is for the fatal failure
// in Subroutine() to abort the entire test.
// The actual behavior: the function goes on after Subroutine() returns.
int* p = NULL;
*p = 3; // Segfault!
}
```
Since we don't use exceptions, it is technically impossible to
implement the intended behavior here. To alleviate this, Google Test
provides two solutions. You could use either the
`(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the
`HasFatalFailure()` function. They are described in the following two
subsections.
### Asserting on Subroutines ###
As shown above, if your test calls a subroutine that has an `ASSERT_*`
failure in it, the test will continue after the subroutine
returns. This may not be what you want.
Often people want fatal failures to propagate like exceptions. For
that Google Test offers the following macros:
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_NO_FATAL_FAILURE(`_statement_`);` | `EXPECT_NO_FATAL_FAILURE(`_statement_`);` | _statement_ doesn't generate any new fatal failures in the current thread. |
Only failures in the thread that executes the assertion are checked to
determine the result of this type of assertions. If _statement_
creates new threads, failures in these threads are ignored.
Examples:
```
ASSERT_NO_FATAL_FAILURE(Foo());
int i;
EXPECT_NO_FATAL_FAILURE({
i = Bar();
});
```
_Availability:_ Linux, Windows, Mac. Assertions from multiple threads
are currently not supported.
### Checking for Failures in the Current Test ###
`HasFatalFailure()` in the `::testing::Test` class returns `true` if an
assertion in the current test has suffered a fatal failure. This
allows functions to catch fatal failures in a sub-routine and return
early.
```
class Test {
public:
...
static bool HasFatalFailure();
};
```
The typical usage, which basically simulates the behavior of a thrown
exception, is:
```
TEST(FooTest, Bar) {
Subroutine();
// Aborts if Subroutine() had a fatal failure.
if (HasFatalFailure())
return;
// The following won't be executed.
...
}
```
If `HasFatalFailure()` is used outside of `TEST()` , `TEST_F()` , or a test
fixture, you must add the `::testing::Test::` prefix, as in:
```
if (::testing::Test::HasFatalFailure())
return;
```
Similarly, `HasNonfatalFailure()` returns `true` if the current test
has at least one non-fatal failure, and `HasFailure()` returns `true`
if the current test has at least one failure of either kind.
_Availability:_ Linux, Windows, Mac. `HasNonfatalFailure()` and
`HasFailure()` are available since version 1.4.0.
# Logging Additional Information #
In your test code, you can call `RecordProperty("key", value)` to log
additional information, where `value` can be either a string or an `int`. The _last_ value recorded for a key will be emitted to the XML output
if you specify one. For example, the test
```
TEST_F(WidgetUsageTest, MinAndMaxWidgets) {
RecordProperty("MaximumWidgets", ComputeMaxUsage());
RecordProperty("MinimumWidgets", ComputeMinUsage());
}
```
will output XML like this:
```
...
<testcase name="MinAndMaxWidgets" status="run" time="6" classname="WidgetUsageTest"
MaximumWidgets="12"
MinimumWidgets="9" />
...
```
_Note_:
* `RecordProperty()` is a static member of the `Test` class. Therefore it needs to be prefixed with `::testing::Test::` if used outside of the `TEST` body and the test fixture class.
* `key` must be a valid XML attribute name, and cannot conflict with the ones already used by Google Test (`name`, `status`, `time`, `classname`, `type_param`, and `value_param`).
* Calling `RecordProperty()` outside of the lifespan of a test is allowed. If it's called outside of a test but between a test case's `SetUpTestCase()` and `TearDownTestCase()` methods, it will be attributed to the XML element for the test case. If it's called outside of all test cases (e.g. in a test environment), it will be attributed to the top-level XML element.
_Availability_: Linux, Windows, Mac.
# Sharing Resources Between Tests in the Same Test Case #
Google Test creates a new test fixture object for each test in order to make
tests independent and easier to debug. However, sometimes tests use resources
that are expensive to set up, making the one-copy-per-test model prohibitively
expensive.
If the tests don't change the resource, there's no harm in them sharing a
single resource copy. So, in addition to per-test set-up/tear-down, Google Test
also supports per-test-case set-up/tear-down. To use it:
1. In your test fixture class (say `FooTest` ), define as `static` some member variables to hold the shared resources.
1. In the same test fixture class, define a `static void SetUpTestCase()` function (remember not to spell it as **`SetupTestCase`** with a small `u`!) to set up the shared resources and a `static void TearDownTestCase()` function to tear them down.
That's it! Google Test automatically calls `SetUpTestCase()` before running the
_first test_ in the `FooTest` test case (i.e. before creating the first
`FooTest` object), and calls `TearDownTestCase()` after running the _last test_
in it (i.e. after deleting the last `FooTest` object). In between, the tests
can use the shared resources.
Remember that the test order is undefined, so your code can't depend on a test
preceding or following another. Also, the tests must either not modify the
state of any shared resource, or, if they do modify the state, they must
restore the state to its original value before passing control to the next
test.
Here's an example of per-test-case set-up and tear-down:
```
class FooTest : public ::testing::Test {
protected:
// Per-test-case set-up.
// Called before the first test in this test case.
// Can be omitted if not needed.
static void SetUpTestCase() {
shared_resource_ = new ...;
}
// Per-test-case tear-down.
// Called after the last test in this test case.
// Can be omitted if not needed.
static void TearDownTestCase() {
delete shared_resource_;
shared_resource_ = NULL;
}
// You can define per-test set-up and tear-down logic as usual.
virtual void SetUp() { ... }
virtual void TearDown() { ... }
// Some expensive resource shared by all tests.
static T* shared_resource_;
};
T* FooTest::shared_resource_ = NULL;
TEST_F(FooTest, Test1) {
... you can refer to shared_resource here ...
}
TEST_F(FooTest, Test2) {
... you can refer to shared_resource here ...
}
```
_Availability:_ Linux, Windows, Mac.
# Global Set-Up and Tear-Down #
Just as you can do set-up and tear-down at the test level and the test case
level, you can also do it at the test program level. Here's how.
First, you subclass the `::testing::Environment` class to define a test
environment, which knows how to set-up and tear-down:
```
class Environment {
public:
virtual ~Environment() {}
// Override this to define how to set up the environment.
virtual void SetUp() {}
// Override this to define how to tear down the environment.
virtual void TearDown() {}
};
```
Then, you register an instance of your environment class with Google Test by
calling the `::testing::AddGlobalTestEnvironment()` function:
```
Environment* AddGlobalTestEnvironment(Environment* env);
```
Now, when `RUN_ALL_TESTS()` is called, it first calls the `SetUp()` method of
the environment object, then runs the tests if there was no fatal failures, and
finally calls `TearDown()` of the environment object.
It's OK to register multiple environment objects. In this case, their `SetUp()`
will be called in the order they are registered, and their `TearDown()` will be
called in the reverse order.
Note that Google Test takes ownership of the registered environment objects.
Therefore **do not delete them** by yourself.
You should call `AddGlobalTestEnvironment()` before `RUN_ALL_TESTS()` is
called, probably in `main()`. If you use `gtest_main`, you need to call
this before `main()` starts for it to take effect. One way to do this is to
define a global variable like this:
```
::testing::Environment* const foo_env = ::testing::AddGlobalTestEnvironment(new FooEnvironment);
```
However, we strongly recommend you to write your own `main()` and call
`AddGlobalTestEnvironment()` there, as relying on initialization of global
variables makes the code harder to read and may cause problems when you
register multiple environments from different translation units and the
environments have dependencies among them (remember that the compiler doesn't
guarantee the order in which global variables from different translation units
are initialized).
_Availability:_ Linux, Windows, Mac.
# Value Parameterized Tests #
_Value-parameterized tests_ allow you to test your code with different
parameters without writing multiple copies of the same test.
Suppose you write a test for your code and then realize that your code is affected by a presence of a Boolean command line flag.
```
TEST(MyCodeTest, TestFoo) {
// A code to test foo().
}
```
Usually people factor their test code into a function with a Boolean parameter in such situations. The function sets the flag, then executes the testing code.
```
void TestFooHelper(bool flag_value) {
flag = flag_value;
// A code to test foo().
}
TEST(MyCodeTest, TestFoo) {
TestFooHelper(false);
TestFooHelper(true);
}
```
But this setup has serious drawbacks. First, when a test assertion fails in your tests, it becomes unclear what value of the parameter caused it to fail. You can stream a clarifying message into your `EXPECT`/`ASSERT` statements, but it you'll have to do it with all of them. Second, you have to add one such helper function per test. What if you have ten tests? Twenty? A hundred?
Value-parameterized tests will let you write your test only once and then easily instantiate and run it with an arbitrary number of parameter values.
Here are some other situations when value-parameterized tests come handy:
* You want to test different implementations of an OO interface.
* You want to test your code over various inputs (a.k.a. data-driven testing). This feature is easy to abuse, so please exercise your good sense when doing it!
## How to Write Value-Parameterized Tests ##
To write value-parameterized tests, first you should define a fixture
class. It must be derived from both `::testing::Test` and
`::testing::WithParamInterface<T>` (the latter is a pure interface),
where `T` is the type of your parameter values. For convenience, you
can just derive the fixture class from `::testing::TestWithParam<T>`,
which itself is derived from both `::testing::Test` and
`::testing::WithParamInterface<T>`. `T` can be any copyable type. If
it's a raw pointer, you are responsible for managing the lifespan of
the pointed values.
```
class FooTest : public ::testing::TestWithParam<const char*> {
// You can implement all the usual fixture class members here.
// To access the test parameter, call GetParam() from class
// TestWithParam<T>.
};
// Or, when you want to add parameters to a pre-existing fixture class:
class BaseTest : public ::testing::Test {
...
};
class BarTest : public BaseTest,
public ::testing::WithParamInterface<const char*> {
...
};
```
Then, use the `TEST_P` macro to define as many test patterns using
this fixture as you want. The `_P` suffix is for "parameterized" or
"pattern", whichever you prefer to think.
```
TEST_P(FooTest, DoesBlah) {
// Inside a test, access the test parameter with the GetParam() method
// of the TestWithParam<T> class:
EXPECT_TRUE(foo.Blah(GetParam()));
...
}
TEST_P(FooTest, HasBlahBlah) {
...
}
```
Finally, you can use `INSTANTIATE_TEST_CASE_P` to instantiate the test
case with any set of parameters you want. Google Test defines a number of
functions for generating test parameters. They return what we call
(surprise!) _parameter generators_. Here is a summary of them,
which are all in the `testing` namespace:
| `Range(begin, end[, step])` | Yields values `{begin, begin+step, begin+step+step, ...}`. The values do not include `end`. `step` defaults to 1. |
|:----------------------------|:------------------------------------------------------------------------------------------------------------------|
| `Values(v1, v2, ..., vN)` | Yields values `{v1, v2, ..., vN}`. |
| `ValuesIn(container)` and `ValuesIn(begin, end)` | Yields values from a C-style array, an STL-style container, or an iterator range `[begin, end)`. `container`, `begin`, and `end` can be expressions whose values are determined at run time. |
| `Bool()` | Yields sequence `{false, true}`. |
| `Combine(g1, g2, ..., gN)` | Yields all combinations (the Cartesian product for the math savvy) of the values generated by the `N` generators. This is only available if your system provides the `<tr1/tuple>` header. If you are sure your system does, and Google Test disagrees, you can override it by defining `GTEST_HAS_TR1_TUPLE=1`. See comments in [include/gtest/internal/gtest-port.h](../include/gtest/internal/gtest-port.h) for more information. |
For more details, see the comments at the definitions of these functions in the [source code](../include/gtest/gtest-param-test.h).
The following statement will instantiate tests from the `FooTest` test case
each with parameter values `"meeny"`, `"miny"`, and `"moe"`.
```
INSTANTIATE_TEST_CASE_P(InstantiationName,
FooTest,
::testing::Values("meeny", "miny", "moe"));
```
To distinguish different instances of the pattern (yes, you can
instantiate it more than once), the first argument to
`INSTANTIATE_TEST_CASE_P` is a prefix that will be added to the actual
test case name. Remember to pick unique prefixes for different
instantiations. The tests from the instantiation above will have these
names:
* `InstantiationName/FooTest.DoesBlah/0` for `"meeny"`
* `InstantiationName/FooTest.DoesBlah/1` for `"miny"`
* `InstantiationName/FooTest.DoesBlah/2` for `"moe"`
* `InstantiationName/FooTest.HasBlahBlah/0` for `"meeny"`
* `InstantiationName/FooTest.HasBlahBlah/1` for `"miny"`
* `InstantiationName/FooTest.HasBlahBlah/2` for `"moe"`
You can use these names in [--gtest\_filter](#running-a-subset-of-the-tests).
This statement will instantiate all tests from `FooTest` again, each
with parameter values `"cat"` and `"dog"`:
```
const char* pets[] = {"cat", "dog"};
INSTANTIATE_TEST_CASE_P(AnotherInstantiationName, FooTest,
::testing::ValuesIn(pets));
```
The tests from the instantiation above will have these names:
* `AnotherInstantiationName/FooTest.DoesBlah/0` for `"cat"`
* `AnotherInstantiationName/FooTest.DoesBlah/1` for `"dog"`
* `AnotherInstantiationName/FooTest.HasBlahBlah/0` for `"cat"`
* `AnotherInstantiationName/FooTest.HasBlahBlah/1` for `"dog"`
Please note that `INSTANTIATE_TEST_CASE_P` will instantiate _all_
tests in the given test case, whether their definitions come before or
_after_ the `INSTANTIATE_TEST_CASE_P` statement.
You can see
[these](../samples/sample7_unittest.cc)
[files](../samples/sample8_unittest.cc) for more examples.
_Availability_: Linux, Windows (requires MSVC 8.0 or above), Mac; since version 1.2.0.
## Creating Value-Parameterized Abstract Tests ##
In the above, we define and instantiate `FooTest` in the same source
file. Sometimes you may want to define value-parameterized tests in a
library and let other people instantiate them later. This pattern is
known as <i>abstract tests</i>. As an example of its application, when you
are designing an interface you can write a standard suite of abstract
tests (perhaps using a factory function as the test parameter) that
all implementations of the interface are expected to pass. When
someone implements the interface, he can instantiate your suite to get
all the interface-conformance tests for free.
To define abstract tests, you should organize your code like this:
1. Put the definition of the parameterized test fixture class (e.g. `FooTest`) in a header file, say `foo_param_test.h`. Think of this as _declaring_ your abstract tests.
1. Put the `TEST_P` definitions in `foo_param_test.cc`, which includes `foo_param_test.h`. Think of this as _implementing_ your abstract tests.
Once they are defined, you can instantiate them by including
`foo_param_test.h`, invoking `INSTANTIATE_TEST_CASE_P()`, and linking
with `foo_param_test.cc`. You can instantiate the same abstract test
case multiple times, possibly in different source files.
# Typed Tests #
Suppose you have multiple implementations of the same interface and
want to make sure that all of them satisfy some common requirements.
Or, you may have defined several types that are supposed to conform to
the same "concept" and you want to verify it. In both cases, you want
the same test logic repeated for different types.
While you can write one `TEST` or `TEST_F` for each type you want to
test (and you may even factor the test logic into a function template
that you invoke from the `TEST`), it's tedious and doesn't scale:
if you want _m_ tests over _n_ types, you'll end up writing _m\*n_
`TEST`s.
_Typed tests_ allow you to repeat the same test logic over a list of
types. You only need to write the test logic once, although you must
know the type list when writing typed tests. Here's how you do it:
First, define a fixture class template. It should be parameterized
by a type. Remember to derive it from `::testing::Test`:
```
template <typename T>
class FooTest : public ::testing::Test {
public:
...
typedef std::list<T> List;
static T shared_;
T value_;
};
```
Next, associate a list of types with the test case, which will be
repeated for each type in the list:
```
typedef ::testing::Types<char, int, unsigned int> MyTypes;
TYPED_TEST_CASE(FooTest, MyTypes);
```
The `typedef` is necessary for the `TYPED_TEST_CASE` macro to parse
correctly. Otherwise the compiler will think that each comma in the
type list introduces a new macro argument.
Then, use `TYPED_TEST()` instead of `TEST_F()` to define a typed test
for this test case. You can repeat this as many times as you want:
```
TYPED_TEST(FooTest, DoesBlah) {
// Inside a test, refer to the special name TypeParam to get the type
// parameter. Since we are inside a derived class template, C++ requires
// us to visit the members of FooTest via 'this'.
TypeParam n = this->value_;
// To visit static members of the fixture, add the 'TestFixture::'
// prefix.
n += TestFixture::shared_;
// To refer to typedefs in the fixture, add the 'typename TestFixture::'
// prefix. The 'typename' is required to satisfy the compiler.
typename TestFixture::List values;
values.push_back(n);
...
}
TYPED_TEST(FooTest, HasPropertyA) { ... }
```
You can see `samples/sample6_unittest.cc` for a complete example.
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Mac;
since version 1.1.0.
# Type-Parameterized Tests #
_Type-parameterized tests_ are like typed tests, except that they
don't require you to know the list of types ahead of time. Instead,
you can define the test logic first and instantiate it with different
type lists later. You can even instantiate it more than once in the
same program.
If you are designing an interface or concept, you can define a suite
of type-parameterized tests to verify properties that any valid
implementation of the interface/concept should have. Then, the author
of each implementation can just instantiate the test suite with his
type to verify that it conforms to the requirements, without having to
write similar tests repeatedly. Here's an example:
First, define a fixture class template, as we did with typed tests:
```
template <typename T>
class FooTest : public ::testing::Test {
...
};
```
Next, declare that you will define a type-parameterized test case:
```
TYPED_TEST_CASE_P(FooTest);
```
The `_P` suffix is for "parameterized" or "pattern", whichever you
prefer to think.
Then, use `TYPED_TEST_P()` to define a type-parameterized test. You
can repeat this as many times as you want:
```
TYPED_TEST_P(FooTest, DoesBlah) {
// Inside a test, refer to TypeParam to get the type parameter.
TypeParam n = 0;
...
}
TYPED_TEST_P(FooTest, HasPropertyA) { ... }
```
Now the tricky part: you need to register all test patterns using the
`REGISTER_TYPED_TEST_CASE_P` macro before you can instantiate them.
The first argument of the macro is the test case name; the rest are
the names of the tests in this test case:
```
REGISTER_TYPED_TEST_CASE_P(FooTest,
DoesBlah, HasPropertyA);
```
Finally, you are free to instantiate the pattern with the types you
want. If you put the above code in a header file, you can `#include`
it in multiple C++ source files and instantiate it multiple times.
```
typedef ::testing::Types<char, int, unsigned int> MyTypes;
INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, MyTypes);
```
To distinguish different instances of the pattern, the first argument
to the `INSTANTIATE_TYPED_TEST_CASE_P` macro is a prefix that will be
added to the actual test case name. Remember to pick unique prefixes
for different instances.
In the special case where the type list contains only one type, you
can write that type directly without `::testing::Types<...>`, like this:
```
INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, int);
```
You can see `samples/sample6_unittest.cc` for a complete example.
_Availability:_ Linux, Windows (requires MSVC 8.0 or above), Mac;
since version 1.1.0.
# Testing Private Code #
If you change your software's internal implementation, your tests should not
break as long as the change is not observable by users. Therefore, per the
_black-box testing principle_, most of the time you should test your code
through its public interfaces.
If you still find yourself needing to test internal implementation code,
consider if there's a better design that wouldn't require you to do so. If you
absolutely have to test non-public interface code though, you can. There are
two cases to consider:
* Static functions (_not_ the same as static member functions!) or unnamed namespaces, and
* Private or protected class members
## Static Functions ##
Both static functions and definitions/declarations in an unnamed namespace are
only visible within the same translation unit. To test them, you can `#include`
the entire `.cc` file being tested in your `*_test.cc` file. (`#include`ing `.cc`
files is not a good way to reuse code - you should not do this in production
code!)
However, a better approach is to move the private code into the
`foo::internal` namespace, where `foo` is the namespace your project normally
uses, and put the private declarations in a `*-internal.h` file. Your
production `.cc` files and your tests are allowed to include this internal
header, but your clients are not. This way, you can fully test your internal
implementation without leaking it to your clients.
## Private Class Members ##
Private class members are only accessible from within the class or by friends.
To access a class' private members, you can declare your test fixture as a
friend to the class and define accessors in your fixture. Tests using the
fixture can then access the private members of your production class via the
accessors in the fixture. Note that even though your fixture is a friend to
your production class, your tests are not automatically friends to it, as they
are technically defined in sub-classes of the fixture.
Another way to test private members is to refactor them into an implementation
class, which is then declared in a `*-internal.h` file. Your clients aren't
allowed to include this header but your tests can. Such is called the Pimpl
(Private Implementation) idiom.
Or, you can declare an individual test as a friend of your class by adding this
line in the class body:
```
FRIEND_TEST(TestCaseName, TestName);
```
For example,
```
// foo.h
#include "gtest/gtest_prod.h"
// Defines FRIEND_TEST.
class Foo {
...
private:
FRIEND_TEST(FooTest, BarReturnsZeroOnNull);
int Bar(void* x);
};
// foo_test.cc
...
TEST(FooTest, BarReturnsZeroOnNull) {
Foo foo;
EXPECT_EQ(0, foo.Bar(NULL));
// Uses Foo's private member Bar().
}
```
Pay special attention when your class is defined in a namespace, as you should
define your test fixtures and tests in the same namespace if you want them to
be friends of your class. For example, if the code to be tested looks like:
```
namespace my_namespace {
class Foo {
friend class FooTest;
FRIEND_TEST(FooTest, Bar);
FRIEND_TEST(FooTest, Baz);
...
definition of the class Foo
...
};
} // namespace my_namespace
```
Your test code should be something like:
```
namespace my_namespace {
class FooTest : public ::testing::Test {
protected:
...
};
TEST_F(FooTest, Bar) { ... }
TEST_F(FooTest, Baz) { ... }
} // namespace my_namespace
```
# Catching Failures #
If you are building a testing utility on top of Google Test, you'll
want to test your utility. What framework would you use to test it?
Google Test, of course.
The challenge is to verify that your testing utility reports failures
correctly. In frameworks that report a failure by throwing an
exception, you could catch the exception and assert on it. But Google
Test doesn't use exceptions, so how do we test that a piece of code
generates an expected failure?
`"gtest/gtest-spi.h"` contains some constructs to do this. After
`#include`ing this header, you can use
| `EXPECT_FATAL_FAILURE(`_statement, substring_`);` |
|:--------------------------------------------------|
to assert that _statement_ generates a fatal (e.g. `ASSERT_*`) failure
whose message contains the given _substring_, or use
| `EXPECT_NONFATAL_FAILURE(`_statement, substring_`);` |
|:-----------------------------------------------------|
if you are expecting a non-fatal (e.g. `EXPECT_*`) failure.
For technical reasons, there are some caveats:
1. You cannot stream a failure message to either macro.
1. _statement_ in `EXPECT_FATAL_FAILURE()` cannot reference local non-static variables or non-static members of `this` object.
1. _statement_ in `EXPECT_FATAL_FAILURE()` cannot return a value.
_Note:_ Google Test is designed with threads in mind. Once the
synchronization primitives in `"gtest/internal/gtest-port.h"` have
been implemented, Google Test will become thread-safe, meaning that
you can then use assertions in multiple threads concurrently. Before
that, however, Google Test only supports single-threaded usage. Once
thread-safe, `EXPECT_FATAL_FAILURE()` and `EXPECT_NONFATAL_FAILURE()`
will capture failures in the current thread only. If _statement_
creates new threads, failures in these threads will be ignored. If
you want to capture failures from all threads instead, you should use
the following macros:
| `EXPECT_FATAL_FAILURE_ON_ALL_THREADS(`_statement, substring_`);` |
|:-----------------------------------------------------------------|
| `EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(`_statement, substring_`);` |
# Getting the Current Test's Name #
Sometimes a function may need to know the name of the currently running test.
For example, you may be using the `SetUp()` method of your test fixture to set
the golden file name based on which test is running. The `::testing::TestInfo`
class has this information:
```
namespace testing {
class TestInfo {
public:
// Returns the test case name and the test name, respectively.
//
// Do NOT delete or free the return value - it's managed by the
// TestInfo class.
const char* test_case_name() const;
const char* name() const;
};
} // namespace testing
```
> To obtain a `TestInfo` object for the currently running test, call
`current_test_info()` on the `UnitTest` singleton object:
```
// Gets information about the currently running test.
// Do NOT delete the returned object - it's managed by the UnitTest class.
const ::testing::TestInfo* const test_info =
::testing::UnitTest::GetInstance()->current_test_info();
printf("We are in test %s of test case %s.\n",
test_info->name(), test_info->test_case_name());
```
`current_test_info()` returns a null pointer if no test is running. In
particular, you cannot find the test case name in `TestCaseSetUp()`,
`TestCaseTearDown()` (where you know the test case name implicitly), or
functions called from them.
_Availability:_ Linux, Windows, Mac.
# Extending Google Test by Handling Test Events #
Google Test provides an <b>event listener API</b> to let you receive
notifications about the progress of a test program and test
failures. The events you can listen to include the start and end of
the test program, a test case, or a test method, among others. You may
use this API to augment or replace the standard console output,
replace the XML output, or provide a completely different form of
output, such as a GUI or a database. You can also use test events as
checkpoints to implement a resource leak checker, for example.
_Availability:_ Linux, Windows, Mac; since v1.4.0.
## Defining Event Listeners ##
To define a event listener, you subclass either
[testing::TestEventListener](../include/gtest/gtest.h#L855)
or [testing::EmptyTestEventListener](../include/gtest/gtest.h#L905).
The former is an (abstract) interface, where <i>each pure virtual method<br>
can be overridden to handle a test event</i> (For example, when a test
starts, the `OnTestStart()` method will be called.). The latter provides
an empty implementation of all methods in the interface, such that a
subclass only needs to override the methods it cares about.
When an event is fired, its context is passed to the handler function
as an argument. The following argument types are used:
* [UnitTest](../include/gtest/gtest.h#L1007) reflects the state of the entire test program,
* [TestCase](../include/gtest/gtest.h#L689) has information about a test case, which can contain one or more tests,
* [TestInfo](../include/gtest/gtest.h#L599) contains the state of a test, and
* [TestPartResult](../include/gtest/gtest-test-part.h#L42) represents the result of a test assertion.
An event handler function can examine the argument it receives to find
out interesting information about the event and the test program's
state. Here's an example:
```
class MinimalistPrinter : public ::testing::EmptyTestEventListener {
// Called before a test starts.
virtual void OnTestStart(const ::testing::TestInfo& test_info) {
printf("*** Test %s.%s starting.\n",
test_info.test_case_name(), test_info.name());
}
// Called after a failed assertion or a SUCCEED() invocation.
virtual void OnTestPartResult(
const ::testing::TestPartResult& test_part_result) {
printf("%s in %s:%d\n%s\n",
test_part_result.failed() ? "*** Failure" : "Success",
test_part_result.file_name(),
test_part_result.line_number(),
test_part_result.summary());
}
// Called after a test ends.
virtual void OnTestEnd(const ::testing::TestInfo& test_info) {
printf("*** Test %s.%s ending.\n",
test_info.test_case_name(), test_info.name());
}
};
```
## Using Event Listeners ##
To use the event listener you have defined, add an instance of it to
the Google Test event listener list (represented by class
[TestEventListeners](../include/gtest/gtest.h#L929)
- note the "s" at the end of the name) in your
`main()` function, before calling `RUN_ALL_TESTS()`:
```
int main(int argc, char** argv) {
::testing::InitGoogleTest(&argc, argv);
// Gets hold of the event listener list.
::testing::TestEventListeners& listeners =
::testing::UnitTest::GetInstance()->listeners();
// Adds a listener to the end. Google Test takes the ownership.
listeners.Append(new MinimalistPrinter);
return RUN_ALL_TESTS();
}
```
There's only one problem: the default test result printer is still in
effect, so its output will mingle with the output from your minimalist
printer. To suppress the default printer, just release it from the
event listener list and delete it. You can do so by adding one line:
```
...
delete listeners.Release(listeners.default_result_printer());
listeners.Append(new MinimalistPrinter);
return RUN_ALL_TESTS();
```
Now, sit back and enjoy a completely different output from your
tests. For more details, you can read this
[sample](../samples/sample9_unittest.cc).
You may append more than one listener to the list. When an `On*Start()`
or `OnTestPartResult()` event is fired, the listeners will receive it in
the order they appear in the list (since new listeners are added to
the end of the list, the default text printer and the default XML
generator will receive the event first). An `On*End()` event will be
received by the listeners in the _reverse_ order. This allows output by
listeners added later to be framed by output from listeners added
earlier.
## Generating Failures in Listeners ##
You may use failure-raising macros (`EXPECT_*()`, `ASSERT_*()`,
`FAIL()`, etc) when processing an event. There are some restrictions:
1. You cannot generate any failure in `OnTestPartResult()` (otherwise it will cause `OnTestPartResult()` to be called recursively).
1. A listener that handles `OnTestPartResult()` is not allowed to generate any failure.
When you add listeners to the listener list, you should put listeners
that handle `OnTestPartResult()` _before_ listeners that can generate
failures. This ensures that failures generated by the latter are
attributed to the right test by the former.
We have a sample of failure-raising listener
[here](../samples/sample10_unittest.cc).
# Running Test Programs: Advanced Options #
Google Test test programs are ordinary executables. Once built, you can run
them directly and affect their behavior via the following environment variables
and/or command line flags. For the flags to work, your programs must call
`::testing::InitGoogleTest()` before calling `RUN_ALL_TESTS()`.
To see a list of supported flags and their usage, please run your test
program with the `--help` flag. You can also use `-h`, `-?`, or `/?`
for short. This feature is added in version 1.3.0.
If an option is specified both by an environment variable and by a
flag, the latter takes precedence. Most of the options can also be
set/read in code: to access the value of command line flag
`--gtest_foo`, write `::testing::GTEST_FLAG(foo)`. A common pattern is
to set the value of a flag before calling `::testing::InitGoogleTest()`
to change the default value of the flag:
```
int main(int argc, char** argv) {
// Disables elapsed time by default.
::testing::GTEST_FLAG(print_time) = false;
// This allows the user to override the flag on the command line.
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
## Selecting Tests ##
This section shows various options for choosing which tests to run.
### Listing Test Names ###
Sometimes it is necessary to list the available tests in a program before
running them so that a filter may be applied if needed. Including the flag
`--gtest_list_tests` overrides all other flags and lists tests in the following
format:
```
TestCase1.
TestName1
TestName2
TestCase2.
TestName
```
None of the tests listed are actually run if the flag is provided. There is no
corresponding environment variable for this flag.
_Availability:_ Linux, Windows, Mac.
### Running a Subset of the Tests ###
By default, a Google Test program runs all tests the user has defined.
Sometimes, you want to run only a subset of the tests (e.g. for debugging or
quickly verifying a change). If you set the `GTEST_FILTER` environment variable
or the `--gtest_filter` flag to a filter string, Google Test will only run the
tests whose full names (in the form of `TestCaseName.TestName`) match the
filter.
The format of a filter is a '`:`'-separated list of wildcard patterns (called
the positive patterns) optionally followed by a '`-`' and another
'`:`'-separated pattern list (called the negative patterns). A test matches the
filter if and only if it matches any of the positive patterns but does not
match any of the negative patterns.
A pattern may contain `'*'` (matches any string) or `'?'` (matches any single
character). For convenience, the filter `'*-NegativePatterns'` can be also
written as `'-NegativePatterns'`.
For example:
* `./foo_test` Has no flag, and thus runs all its tests.
* `./foo_test --gtest_filter=*` Also runs everything, due to the single match-everything `*` value.
* `./foo_test --gtest_filter=FooTest.*` Runs everything in test case `FooTest`.
* `./foo_test --gtest_filter=*Null*:*Constructor*` Runs any test whose full name contains either `"Null"` or `"Constructor"`.
* `./foo_test --gtest_filter=-*DeathTest.*` Runs all non-death tests.
* `./foo_test --gtest_filter=FooTest.*-FooTest.Bar` Runs everything in test case `FooTest` except `FooTest.Bar`.
_Availability:_ Linux, Windows, Mac.
### Temporarily Disabling Tests ###
If you have a broken test that you cannot fix right away, you can add the
`DISABLED_` prefix to its name. This will exclude it from execution. This is
better than commenting out the code or using `#if 0`, as disabled tests are
still compiled (and thus won't rot).
If you need to disable all tests in a test case, you can either add `DISABLED_`
to the front of the name of each test, or alternatively add it to the front of
the test case name.
For example, the following tests won't be run by Google Test, even though they
will still be compiled:
```
// Tests that Foo does Abc.
TEST(FooTest, DISABLED_DoesAbc) { ... }
class DISABLED_BarTest : public ::testing::Test { ... };
// Tests that Bar does Xyz.
TEST_F(DISABLED_BarTest, DoesXyz) { ... }
```
_Note:_ This feature should only be used for temporary pain-relief. You still
have to fix the disabled tests at a later date. As a reminder, Google Test will
print a banner warning you if a test program contains any disabled tests.
_Tip:_ You can easily count the number of disabled tests you have
using `grep`. This number can be used as a metric for improving your
test quality.
_Availability:_ Linux, Windows, Mac.
### Temporarily Enabling Disabled Tests ###
To include [disabled tests](#temporarily-disabling-tests) in test
execution, just invoke the test program with the
`--gtest_also_run_disabled_tests` flag or set the
`GTEST_ALSO_RUN_DISABLED_TESTS` environment variable to a value other
than `0`. You can combine this with the
[--gtest\_filter](#running-a-subset-of-the-tests) flag to further select
which disabled tests to run.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
## Repeating the Tests ##
Once in a while you'll run into a test whose result is hit-or-miss. Perhaps it
will fail only 1% of the time, making it rather hard to reproduce the bug under
a debugger. This can be a major source of frustration.
The `--gtest_repeat` flag allows you to repeat all (or selected) test methods
in a program many times. Hopefully, a flaky test will eventually fail and give
you a chance to debug. Here's how to use it:
| `$ foo_test --gtest_repeat=1000` | Repeat foo\_test 1000 times and don't stop at failures. |
|:---------------------------------|:--------------------------------------------------------|
| `$ foo_test --gtest_repeat=-1` | A negative count means repeating forever. |
| `$ foo_test --gtest_repeat=1000 --gtest_break_on_failure` | Repeat foo\_test 1000 times, stopping at the first failure. This is especially useful when running under a debugger: when the testfails, it will drop into the debugger and you can then inspect variables and stacks. |
| `$ foo_test --gtest_repeat=1000 --gtest_filter=FooBar` | Repeat the tests whose name matches the filter 1000 times. |
If your test program contains global set-up/tear-down code registered
using `AddGlobalTestEnvironment()`, it will be repeated in each
iteration as well, as the flakiness may be in it. You can also specify
the repeat count by setting the `GTEST_REPEAT` environment variable.
_Availability:_ Linux, Windows, Mac.
## Shuffling the Tests ##
You can specify the `--gtest_shuffle` flag (or set the `GTEST_SHUFFLE`
environment variable to `1`) to run the tests in a program in a random
order. This helps to reveal bad dependencies between tests.
By default, Google Test uses a random seed calculated from the current
time. Therefore you'll get a different order every time. The console
output includes the random seed value, such that you can reproduce an
order-related test failure later. To specify the random seed
explicitly, use the `--gtest_random_seed=SEED` flag (or set the
`GTEST_RANDOM_SEED` environment variable), where `SEED` is an integer
between 0 and 99999. The seed value 0 is special: it tells Google Test
to do the default behavior of calculating the seed from the current
time.
If you combine this with `--gtest_repeat=N`, Google Test will pick a
different random seed and re-shuffle the tests in each iteration.
_Availability:_ Linux, Windows, Mac; since v1.4.0.
## Controlling Test Output ##
This section teaches how to tweak the way test results are reported.
### Colored Terminal Output ###
Google Test can use colors in its terminal output to make it easier to spot
the separation between tests, and whether tests passed.
You can set the GTEST\_COLOR environment variable or set the `--gtest_color`
command line flag to `yes`, `no`, or `auto` (the default) to enable colors,
disable colors, or let Google Test decide. When the value is `auto`, Google
Test will use colors if and only if the output goes to a terminal and (on
non-Windows platforms) the `TERM` environment variable is set to `xterm` or
`xterm-color`.
_Availability:_ Linux, Windows, Mac.
### Suppressing the Elapsed Time ###
By default, Google Test prints the time it takes to run each test. To
suppress that, run the test program with the `--gtest_print_time=0`
command line flag. Setting the `GTEST_PRINT_TIME` environment
variable to `0` has the same effect.
_Availability:_ Linux, Windows, Mac. (In Google Test 1.3.0 and lower,
the default behavior is that the elapsed time is **not** printed.)
### Generating an XML Report ###
Google Test can emit a detailed XML report to a file in addition to its normal
textual output. The report contains the duration of each test, and thus can
help you identify slow tests.
To generate the XML report, set the `GTEST_OUTPUT` environment variable or the
`--gtest_output` flag to the string `"xml:_path_to_output_file_"`, which will
create the file at the given location. You can also just use the string
`"xml"`, in which case the output can be found in the `test_detail.xml` file in
the current directory.
If you specify a directory (for example, `"xml:output/directory/"` on Linux or
`"xml:output\directory\"` on Windows), Google Test will create the XML file in
that directory, named after the test executable (e.g. `foo_test.xml` for test
program `foo_test` or `foo_test.exe`). If the file already exists (perhaps left
over from a previous run), Google Test will pick a different name (e.g.
`foo_test_1.xml`) to avoid overwriting it.
The report uses the format described here. It is based on the
`junitreport` Ant task and can be parsed by popular continuous build
systems like [Jenkins](http://jenkins-ci.org/). Since that format
was originally intended for Java, a little interpretation is required
to make it apply to Google Test tests, as shown here:
```
<testsuites name="AllTests" ...>
<testsuite name="test_case_name" ...>
<testcase name="test_name" ...>
<failure message="..."/>
<failure message="..."/>
<failure message="..."/>
</testcase>
</testsuite>
</testsuites>
```
* The root `<testsuites>` element corresponds to the entire test program.
* `<testsuite>` elements correspond to Google Test test cases.
* `<testcase>` elements correspond to Google Test test functions.
For instance, the following program
```
TEST(MathTest, Addition) { ... }
TEST(MathTest, Subtraction) { ... }
TEST(LogicTest, NonContradiction) { ... }
```
could generate this report:
```
<?xml version="1.0" encoding="UTF-8"?>
<testsuites tests="3" failures="1" errors="0" time="35" name="AllTests">
<testsuite name="MathTest" tests="2" failures="1" errors="0" time="15">
<testcase name="Addition" status="run" time="7" classname="">
<failure message="Value of: add(1, 1)&#x0A; Actual: 3&#x0A;Expected: 2" type=""/>
<failure message="Value of: add(1, -1)&#x0A; Actual: 1&#x0A;Expected: 0" type=""/>
</testcase>
<testcase name="Subtraction" status="run" time="5" classname="">
</testcase>
</testsuite>
<testsuite name="LogicTest" tests="1" failures="0" errors="0" time="5">
<testcase name="NonContradiction" status="run" time="5" classname="">
</testcase>
</testsuite>
</testsuites>
```
Things to note:
* The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how many test functions the Google Test program or test case contains, while the `failures` attribute tells how many of them failed.
* The `time` attribute expresses the duration of the test, test case, or entire test program in milliseconds.
* Each `<failure>` element corresponds to a single failed Google Test assertion.
* Some JUnit concepts don't apply to Google Test, yet we have to conform to the DTD. Therefore you'll see some dummy elements and attributes in the report. You can safely ignore these parts.
_Availability:_ Linux, Windows, Mac.
## Controlling How Failures Are Reported ##
### Turning Assertion Failures into Break-Points ###
When running test programs under a debugger, it's very convenient if the
debugger can catch an assertion failure and automatically drop into interactive
mode. Google Test's _break-on-failure_ mode supports this behavior.
To enable it, set the `GTEST_BREAK_ON_FAILURE` environment variable to a value
other than `0` . Alternatively, you can use the `--gtest_break_on_failure`
command line flag.
_Availability:_ Linux, Windows, Mac.
### Disabling Catching Test-Thrown Exceptions ###
Google Test can be used either with or without exceptions enabled. If
a test throws a C++ exception or (on Windows) a structured exception
(SEH), by default Google Test catches it, reports it as a test
failure, and continues with the next test method. This maximizes the
coverage of a test run. Also, on Windows an uncaught exception will
cause a pop-up window, so catching the exceptions allows you to run
the tests automatically.
When debugging the test failures, however, you may instead want the
exceptions to be handled by the debugger, such that you can examine
the call stack when an exception is thrown. To achieve that, set the
`GTEST_CATCH_EXCEPTIONS` environment variable to `0`, or use the
`--gtest_catch_exceptions=0` flag when running the tests.
**Availability**: Linux, Windows, Mac.
### Letting Another Testing Framework Drive ###
If you work on a project that has already been using another testing
framework and is not ready to completely switch to Google Test yet,
you can get much of Google Test's benefit by using its assertions in
your existing tests. Just change your `main()` function to look
like:
```
#include "gtest/gtest.h"
int main(int argc, char** argv) {
::testing::GTEST_FLAG(throw_on_failure) = true;
// Important: Google Test must be initialized.
::testing::InitGoogleTest(&argc, argv);
... whatever your existing testing framework requires ...
}
```
With that, you can use Google Test assertions in addition to the
native assertions your testing framework provides, for example:
```
void TestFooDoesBar() {
Foo foo;
EXPECT_LE(foo.Bar(1), 100); // A Google Test assertion.
CPPUNIT_ASSERT(foo.IsEmpty()); // A native assertion.
}
```
If a Google Test assertion fails, it will print an error message and
throw an exception, which will be treated as a failure by your host
testing framework. If you compile your code with exceptions disabled,
a failed Google Test assertion will instead exit your program with a
non-zero code, which will also signal a test failure to your test
runner.
If you don't write `::testing::GTEST_FLAG(throw_on_failure) = true;` in
your `main()`, you can alternatively enable this feature by specifying
the `--gtest_throw_on_failure` flag on the command-line or setting the
`GTEST_THROW_ON_FAILURE` environment variable to a non-zero value.
Death tests are _not_ supported when other test framework is used to organize tests.
_Availability:_ Linux, Windows, Mac; since v1.3.0.
## Distributing Test Functions to Multiple Machines ##
If you have more than one machine you can use to run a test program,
you might want to run the test functions in parallel and get the
result faster. We call this technique _sharding_, where each machine
is called a _shard_.
Google Test is compatible with test sharding. To take advantage of
this feature, your test runner (not part of Google Test) needs to do
the following:
1. Allocate a number of machines (shards) to run the tests.
1. On each shard, set the `GTEST_TOTAL_SHARDS` environment variable to the total number of shards. It must be the same for all shards.
1. On each shard, set the `GTEST_SHARD_INDEX` environment variable to the index of the shard. Different shards must be assigned different indices, which must be in the range `[0, GTEST_TOTAL_SHARDS - 1]`.
1. Run the same test program on all shards. When Google Test sees the above two environment variables, it will select a subset of the test functions to run. Across all shards, each test function in the program will be run exactly once.
1. Wait for all shards to finish, then collect and report the results.
Your project may have tests that were written without Google Test and
thus don't understand this protocol. In order for your test runner to
figure out which test supports sharding, it can set the environment
variable `GTEST_SHARD_STATUS_FILE` to a non-existent file path. If a
test program supports sharding, it will create this file to
acknowledge the fact (the actual contents of the file are not
important at this time; although we may stick some useful information
in it in the future.); otherwise it will not create it.
Here's an example to make it clear. Suppose you have a test program
`foo_test` that contains the following 5 test functions:
```
TEST(A, V)
TEST(A, W)
TEST(B, X)
TEST(B, Y)
TEST(B, Z)
```
and you have 3 machines at your disposal. To run the test functions in
parallel, you would set `GTEST_TOTAL_SHARDS` to 3 on all machines, and
set `GTEST_SHARD_INDEX` to 0, 1, and 2 on the machines respectively.
Then you would run the same `foo_test` on each machine.
Google Test reserves the right to change how the work is distributed
across the shards, but here's one possible scenario:
* Machine #0 runs `A.V` and `B.X`.
* Machine #1 runs `A.W` and `B.Y`.
* Machine #2 runs `B.Z`.
_Availability:_ Linux, Windows, Mac; since version 1.3.0.
# Fusing Google Test Source Files #
Google Test's implementation consists of ~30 files (excluding its own
tests). Sometimes you may want them to be packaged up in two files (a
`.h` and a `.cc`) instead, such that you can easily copy them to a new
machine and start hacking there. For this we provide an experimental
Python script `fuse_gtest_files.py` in the `scripts/` directory (since release 1.3.0).
Assuming you have Python 2.4 or above installed on your machine, just
go to that directory and run
```
python fuse_gtest_files.py OUTPUT_DIR
```
and you should see an `OUTPUT_DIR` directory being created with files
`gtest/gtest.h` and `gtest/gtest-all.cc` in it. These files contain
everything you need to use Google Test. Just copy them to anywhere
you want and you are ready to write tests. You can use the
[scripts/test/Makefile](../scripts/test/Makefile)
file as an example on how to compile your tests against them.
# Where to Go from Here #
Congratulations! You've now learned more advanced Google Test tools and are
ready to tackle more complex testing tasks. If you want to dive even deeper, you
can read the [Frequently-Asked Questions](V1_7_FAQ.md).
googletest/docs/V1_7_Documentation.md deleted 100644 → 0
View file @ 15790643
This page lists all documentation wiki pages for Google Test **(the SVN trunk version)**
-- **if you use a released version of Google Test, please read the
documentation for that specific version instead.**
* [Primer](V1_7_Primer.md) -- start here if you are new to Google Test.
* [Samples](V1_7_Samples.md) -- learn from examples.
* [AdvancedGuide](V1_7_AdvancedGuide.md) -- learn more about Google Test.
* [XcodeGuide](V1_7_XcodeGuide.md) -- how to use Google Test in Xcode on Mac.
* [Frequently-Asked Questions](V1_7_FAQ.md) -- check here before asking a question on the mailing list.
To contribute code to Google Test, read:
* [DevGuide](DevGuide.md) -- read this _before_ writing your first patch.
* [PumpManual](V1_7_PumpManual.md) -- how we generate some of Google Test's source files.
\ No newline at end of file
googletest/docs/V1_7_FAQ.md deleted 100644 → 0
View file @ 15790643
If you cannot find the answer to your question here, and you have read
[Primer](V1_7_Primer.md) and [AdvancedGuide](V1_7_AdvancedGuide.md), send it to
googletestframework@googlegroups.com.
## Why should I use Google Test instead of my favorite C++ testing framework? ##
First, let us say clearly that we don't want to get into the debate of
which C++ testing framework is **the best**. There exist many fine
frameworks for writing C++ tests, and we have tremendous respect for
the developers and users of them. We don't think there is (or will
be) a single best framework - you have to pick the right tool for the
particular task you are tackling.
We created Google Test because we couldn't find the right combination
of features and conveniences in an existing framework to satisfy _our_
needs. The following is a list of things that _we_ like about Google
Test. We don't claim them to be unique to Google Test - rather, the
combination of them makes Google Test the choice for us. We hope this
list can help you decide whether it is for you too.
* Google Test is designed to be portable: it doesn't require exceptions or RTTI; it works around various bugs in various compilers and environments; etc. As a result, it works on Linux, Mac OS X, Windows and several embedded operating systems.
* Nonfatal assertions (`EXPECT_*`) have proven to be great time savers, as they allow a test to report multiple failures in a single edit-compile-test cycle.
* It's easy to write assertions that generate informative messages: you just use the stream syntax to append any additional information, e.g. `ASSERT_EQ(5, Foo(i)) << " where i = " << i;`. It doesn't require a new set of macros or special functions.
* Google Test automatically detects your tests and doesn't require you to enumerate them in order to run them.
* Death tests are pretty handy for ensuring that your asserts in production code are triggered by the right conditions.
* `SCOPED_TRACE` helps you understand the context of an assertion failure when it comes from inside a sub-routine or loop.
* You can decide which tests to run using name patterns. This saves time when you want to quickly reproduce a test failure.
* Google Test can generate XML test result reports that can be parsed by popular continuous build system like Hudson.
* Simple things are easy in Google Test, while hard things are possible: in addition to advanced features like [global test environments](V1_7_AdvancedGuide.md#global-set-up-and-tear-down) and tests parameterized by [values](V1_7_AdvancedGuide.md#value-parameterized-tests) or [types](V1_7_AdvancedGuide.md#typed-tests), Google Test supports various ways for the user to extend the framework -- if Google Test doesn't do something out of the box, chances are that a user can implement the feature using Google Test's public API, without changing Google Test itself. In particular, you can:
* expand your testing vocabulary by defining [custom predicates](V1_7_AdvancedGuide.md#predicate-assertions-for-better-error-messages),
* teach Google Test how to [print your types](V1_7_AdvancedGuide.md#teaching-google-test-how-to-print-your-values),
* define your own testing macros or utilities and verify them using Google Test's [Service Provider Interface](V1_7_AdvancedGuide.md#catching-failures), and
* reflect on the test cases or change the test output format by intercepting the [test events](V1_7_AdvancedGuide.md#extending-google-test-by-handling-test-events).
## I'm getting warnings when compiling Google Test. Would you fix them? ##
We strive to minimize compiler warnings Google Test generates. Before releasing a new version, we test to make sure that it doesn't generate warnings when compiled using its CMake script on Windows, Linux, and Mac OS.
Unfortunately, this doesn't mean you are guaranteed to see no warnings when compiling Google Test in your environment:
* You may be using a different compiler as we use, or a different version of the same compiler. We cannot possibly test for all compilers.
* You may be compiling on a different platform as we do.
* Your project may be using different compiler flags as we do.
It is not always possible to make Google Test warning-free for everyone. Or, it may not be desirable if the warning is rarely enabled and fixing the violations makes the code more complex.
If you see warnings when compiling Google Test, we suggest that you use the `-isystem` flag (assuming your are using GCC) to mark Google Test headers as system headers. That'll suppress warnings from Google Test headers.
## Why should not test case names and test names contain underscore? ##
Underscore (`_`) is special, as C++ reserves the following to be used by
the compiler and the standard library:
1. any identifier that starts with an `_` followed by an upper-case letter, and
1. any identifier that containers two consecutive underscores (i.e. `__`) _anywhere_ in its name.
User code is _prohibited_ from using such identifiers.
Now let's look at what this means for `TEST` and `TEST_F`.
Currently `TEST(TestCaseName, TestName)` generates a class named
`TestCaseName_TestName_Test`. What happens if `TestCaseName` or `TestName`
contains `_`?
1. If `TestCaseName` starts with an `_` followed by an upper-case letter (say, `_Foo`), we end up with `_Foo_TestName_Test`, which is reserved and thus invalid.
1. If `TestCaseName` ends with an `_` (say, `Foo_`), we get `Foo__TestName_Test`, which is invalid.
1. If `TestName` starts with an `_` (say, `_Bar`), we get `TestCaseName__Bar_Test`, which is invalid.
1. If `TestName` ends with an `_` (say, `Bar_`), we get `TestCaseName_Bar__Test`, which is invalid.
So clearly `TestCaseName` and `TestName` cannot start or end with `_`
(Actually, `TestCaseName` can start with `_` -- as long as the `_` isn't
followed by an upper-case letter. But that's getting complicated. So
for simplicity we just say that it cannot start with `_`.).
It may seem fine for `TestCaseName` and `TestName` to contain `_` in the
middle. However, consider this:
```
TEST(Time, Flies_Like_An_Arrow) { ... }
TEST(Time_Flies, Like_An_Arrow) { ... }
```
Now, the two `TEST`s will both generate the same class
(`Time_Files_Like_An_Arrow_Test`). That's not good.
So for simplicity, we just ask the users to avoid `_` in `TestCaseName`
and `TestName`. The rule is more constraining than necessary, but it's
simple and easy to remember. It also gives Google Test some wiggle
room in case its implementation needs to change in the future.
If you violate the rule, there may not be immediately consequences,
but your test may (just may) break with a new compiler (or a new
version of the compiler you are using) or with a new version of Google
Test. Therefore it's best to follow the rule.
## Why is it not recommended to install a pre-compiled copy of Google Test (for example, into /usr/local)? ##
In the early days, we said that you could install
compiled Google Test libraries on `*`nix systems using `make install`.
Then every user of your machine can write tests without
recompiling Google Test.
This seemed like a good idea, but it has a
got-cha: every user needs to compile his tests using the _same_ compiler
flags used to compile the installed Google Test libraries; otherwise
he may run into undefined behaviors (i.e. the tests can behave
strangely and may even crash for no obvious reasons).
Why? Because C++ has this thing called the One-Definition Rule: if
two C++ source files contain different definitions of the same
class/function/variable, and you link them together, you violate the
rule. The linker may or may not catch the error (in many cases it's
not required by the C++ standard to catch the violation). If it
doesn't, you get strange run-time behaviors that are unexpected and
hard to debug.
If you compile Google Test and your test code using different compiler
flags, they may see different definitions of the same
class/function/variable (e.g. due to the use of `#if` in Google Test).
Therefore, for your sanity, we recommend to avoid installing pre-compiled
Google Test libraries. Instead, each project should compile
Google Test itself such that it can be sure that the same flags are
used for both Google Test and the tests.
## How do I generate 64-bit binaries on Windows (using Visual Studio 2008)? ##
(Answered by Trevor Robinson)
Load the supplied Visual Studio solution file, either `msvc\gtest-md.sln` or
`msvc\gtest.sln`. Go through the migration wizard to migrate the
solution and project files to Visual Studio 2008. Select
`Configuration Manager...` from the `Build` menu. Select `<New...>` from
the `Active solution platform` dropdown. Select `x64` from the new
platform dropdown, leave `Copy settings from` set to `Win32` and
`Create new project platforms` checked, then click `OK`. You now have
`Win32` and `x64` platform configurations, selectable from the
`Standard` toolbar, which allow you to toggle between building 32-bit or
64-bit binaries (or both at once using Batch Build).
In order to prevent build output files from overwriting one another,
you'll need to change the `Intermediate Directory` settings for the
newly created platform configuration across all the projects. To do
this, multi-select (e.g. using shift-click) all projects (but not the
solution) in the `Solution Explorer`. Right-click one of them and
select `Properties`. In the left pane, select `Configuration Properties`,
and from the `Configuration` dropdown, select `All Configurations`.
Make sure the selected platform is `x64`. For the
`Intermediate Directory` setting, change the value from
`$(PlatformName)\$(ConfigurationName)` to
`$(OutDir)\$(ProjectName)`. Click `OK` and then build the
solution. When the build is complete, the 64-bit binaries will be in
the `msvc\x64\Debug` directory.
## Can I use Google Test on MinGW? ##
We haven't tested this ourselves, but Per Abrahamsen reported that he
was able to compile and install Google Test successfully when using
MinGW from Cygwin. You'll need to configure it with:
`PATH/TO/configure CC="gcc -mno-cygwin" CXX="g++ -mno-cygwin"`
You should be able to replace the `-mno-cygwin` option with direct links
to the real MinGW binaries, but we haven't tried that.
Caveats:
* There are many warnings when compiling.
* `make check` will produce some errors as not all tests for Google Test itself are compatible with MinGW.
We also have reports on successful cross compilation of Google Test
MinGW binaries on Linux using
[these instructions](http://wiki.wxwidgets.org/Cross-Compiling_Under_Linux#Cross-compiling_under_Linux_for_MS_Windows)
on the WxWidgets site.
Please contact `googletestframework@googlegroups.com` if you are
interested in improving the support for MinGW.
## Why does Google Test support EXPECT\_EQ(NULL, ptr) and ASSERT\_EQ(NULL, ptr) but not EXPECT\_NE(NULL, ptr) and ASSERT\_NE(NULL, ptr)? ##
Due to some peculiarity of C++, it requires some non-trivial template
meta programming tricks to support using `NULL` as an argument of the
`EXPECT_XX()` and `ASSERT_XX()` macros. Therefore we only do it where
it's most needed (otherwise we make the implementation of Google Test
harder to maintain and more error-prone than necessary).
The `EXPECT_EQ()` macro takes the _expected_ value as its first
argument and the _actual_ value as the second. It's reasonable that
someone wants to write `EXPECT_EQ(NULL, some_expression)`, and this
indeed was requested several times. Therefore we implemented it.
The need for `EXPECT_NE(NULL, ptr)` isn't nearly as strong. When the
assertion fails, you already know that `ptr` must be `NULL`, so it
doesn't add any information to print ptr in this case. That means
`EXPECT_TRUE(ptr != NULL)` works just as well.
If we were to support `EXPECT_NE(NULL, ptr)`, for consistency we'll
have to support `EXPECT_NE(ptr, NULL)` as well, as unlike `EXPECT_EQ`,
we don't have a convention on the order of the two arguments for
`EXPECT_NE`. This means using the template meta programming tricks
twice in the implementation, making it even harder to understand and
maintain. We believe the benefit doesn't justify the cost.
Finally, with the growth of Google Mock's [matcher](../../CookBook.md#using-matchers-in-google-test-assertions) library, we are
encouraging people to use the unified `EXPECT_THAT(value, matcher)`
syntax more often in tests. One significant advantage of the matcher
approach is that matchers can be easily combined to form new matchers,
while the `EXPECT_NE`, etc, macros cannot be easily
combined. Therefore we want to invest more in the matchers than in the
`EXPECT_XX()` macros.
## Does Google Test support running tests in parallel? ##
Test runners tend to be tightly coupled with the build/test
environment, and Google Test doesn't try to solve the problem of
running tests in parallel. Instead, we tried to make Google Test work
nicely with test runners. For example, Google Test's XML report
contains the time spent on each test, and its `gtest_list_tests` and
`gtest_filter` flags can be used for splitting the execution of test
methods into multiple processes. These functionalities can help the
test runner run the tests in parallel.
## Why don't Google Test run the tests in different threads to speed things up? ##
It's difficult to write thread-safe code. Most tests are not written
with thread-safety in mind, and thus may not work correctly in a
multi-threaded setting.
If you think about it, it's already hard to make your code work when
you know what other threads are doing. It's much harder, and
sometimes even impossible, to make your code work when you don't know
what other threads are doing (remember that test methods can be added,
deleted, or modified after your test was written). If you want to run
the tests in parallel, you'd better run them in different processes.
## Why aren't Google Test assertions implemented using exceptions? ##
Our original motivation was to be able to use Google Test in projects
that disable exceptions. Later we realized some additional benefits
of this approach:
1. Throwing in a destructor is undefined behavior in C++. Not using exceptions means Google Test's assertions are safe to use in destructors.
1. The `EXPECT_*` family of macros will continue even after a failure, allowing multiple failures in a `TEST` to be reported in a single run. This is a popular feature, as in C++ the edit-compile-test cycle is usually quite long and being able to fixing more than one thing at a time is a blessing.
1. If assertions are implemented using exceptions, a test may falsely ignore a failure if it's caught by user code:
```
try { ... ASSERT_TRUE(...) ... }
catch (...) { ... }
```
The above code will pass even if the `ASSERT_TRUE` throws. While it's unlikely for someone to write this in a test, it's possible to run into this pattern when you write assertions in callbacks that are called by the code under test.
The downside of not using exceptions is that `ASSERT_*` (implemented
using `return`) will only abort the current function, not the current
`TEST`.
## Why do we use two different macros for tests with and without fixtures? ##
Unfortunately, C++'s macro system doesn't allow us to use the same
macro for both cases. One possibility is to provide only one macro
for tests with fixtures, and require the user to define an empty
fixture sometimes:
```
class FooTest : public ::testing::Test {};
TEST_F(FooTest, DoesThis) { ... }
```
or
```
typedef ::testing::Test FooTest;
TEST_F(FooTest, DoesThat) { ... }
```
Yet, many people think this is one line too many. :-) Our goal was to
make it really easy to write tests, so we tried to make simple tests
trivial to create. That means using a separate macro for such tests.
We think neither approach is ideal, yet either of them is reasonable.
In the end, it probably doesn't matter much either way.
## Why don't we use structs as test fixtures? ##
We like to use structs only when representing passive data. This
distinction between structs and classes is good for documenting the
intent of the code's author. Since test fixtures have logic like
`SetUp()` and `TearDown()`, they are better defined as classes.
## Why are death tests implemented as assertions instead of using a test runner? ##
Our goal was to make death tests as convenient for a user as C++
possibly allows. In particular:
* The runner-style requires to split the information into two pieces: the definition of the death test itself, and the specification for the runner on how to run the death test and what to expect. The death test would be written in C++, while the runner spec may or may not be. A user needs to carefully keep the two in sync. `ASSERT_DEATH(statement, expected_message)` specifies all necessary information in one place, in one language, without boilerplate code. It is very declarative.
* `ASSERT_DEATH` has a similar syntax and error-reporting semantics as other Google Test assertions, and thus is easy to learn.
* `ASSERT_DEATH` can be mixed with other assertions and other logic at your will. You are not limited to one death test per test method. For example, you can write something like:
```
if (FooCondition()) {
ASSERT_DEATH(Bar(), "blah");
} else {
ASSERT_EQ(5, Bar());
}
```
If you prefer one death test per test method, you can write your tests in that style too, but we don't want to impose that on the users. The fewer artificial limitations the better.
* `ASSERT_DEATH` can reference local variables in the current function, and you can decide how many death tests you want based on run-time information. For example,
```
const int count = GetCount(); // Only known at run time.
for (int i = 1; i <= count; i++) {
ASSERT_DEATH({
double* buffer = new double[i];
... initializes buffer ...
Foo(buffer, i)
}, "blah blah");
}
```
The runner-based approach tends to be more static and less flexible, or requires more user effort to get this kind of flexibility.
Another interesting thing about `ASSERT_DEATH` is that it calls `fork()`
to create a child process to run the death test. This is lightening
fast, as `fork()` uses copy-on-write pages and incurs almost zero
overhead, and the child process starts from the user-supplied
statement directly, skipping all global and local initialization and
any code leading to the given statement. If you launch the child
process from scratch, it can take seconds just to load everything and
start running if the test links to many libraries dynamically.
## My death test modifies some state, but the change seems lost after the death test finishes. Why? ##
Death tests (`EXPECT_DEATH`, etc) are executed in a sub-process s.t. the
expected crash won't kill the test program (i.e. the parent process). As a
result, any in-memory side effects they incur are observable in their
respective sub-processes, but not in the parent process. You can think of them
as running in a parallel universe, more or less.
## The compiler complains about "undefined references" to some static const member variables, but I did define them in the class body. What's wrong? ##
If your class has a static data member:
```
// foo.h
class Foo {
...
static const int kBar = 100;
};
```
You also need to define it _outside_ of the class body in `foo.cc`:
```
const int Foo::kBar; // No initializer here.
```
Otherwise your code is **invalid C++**, and may break in unexpected ways. In
particular, using it in Google Test comparison assertions (`EXPECT_EQ`, etc)
will generate an "undefined reference" linker error.
## I have an interface that has several implementations. Can I write a set of tests once and repeat them over all the implementations? ##
Google Test doesn't yet have good support for this kind of tests, or
data-driven tests in general. We hope to be able to make improvements in this
area soon.
## Can I derive a test fixture from another? ##
Yes.
Each test fixture has a corresponding and same named test case. This means only
one test case can use a particular fixture. Sometimes, however, multiple test
cases may want to use the same or slightly different fixtures. For example, you
may want to make sure that all of a GUI library's test cases don't leak
important system resources like fonts and brushes.
In Google Test, you share a fixture among test cases by putting the shared
logic in a base test fixture, then deriving from that base a separate fixture
for each test case that wants to use this common logic. You then use `TEST_F()`
to write tests using each derived fixture.
Typically, your code looks like this:
```
// Defines a base test fixture.
class BaseTest : public ::testing::Test {
protected:
...
};
// Derives a fixture FooTest from BaseTest.
class FooTest : public BaseTest {
protected:
virtual void SetUp() {
BaseTest::SetUp(); // Sets up the base fixture first.
... additional set-up work ...
}
virtual void TearDown() {
... clean-up work for FooTest ...
BaseTest::TearDown(); // Remember to tear down the base fixture
// after cleaning up FooTest!
}
... functions and variables for FooTest ...
};
// Tests that use the fixture FooTest.
TEST_F(FooTest, Bar) { ... }
TEST_F(FooTest, Baz) { ... }
... additional fixtures derived from BaseTest ...
```
If necessary, you can continue to derive test fixtures from a derived fixture.
Google Test has no limit on how deep the hierarchy can be.
For a complete example using derived test fixtures, see
[sample5](../samples/sample5_unittest.cc).
## My compiler complains "void value not ignored as it ought to be." What does this mean? ##
You're probably using an `ASSERT_*()` in a function that doesn't return `void`.
`ASSERT_*()` can only be used in `void` functions.
## My death test hangs (or seg-faults). How do I fix it? ##
In Google Test, death tests are run in a child process and the way they work is
delicate. To write death tests you really need to understand how they work.
Please make sure you have read this.
In particular, death tests don't like having multiple threads in the parent
process. So the first thing you can try is to eliminate creating threads
outside of `EXPECT_DEATH()`.
Sometimes this is impossible as some library you must use may be creating
threads before `main()` is even reached. In this case, you can try to minimize
the chance of conflicts by either moving as many activities as possible inside
`EXPECT_DEATH()` (in the extreme case, you want to move everything inside), or
leaving as few things as possible in it. Also, you can try to set the death
test style to `"threadsafe"`, which is safer but slower, and see if it helps.
If you go with thread-safe death tests, remember that they rerun the test
program from the beginning in the child process. Therefore make sure your
program can run side-by-side with itself and is deterministic.
In the end, this boils down to good concurrent programming. You have to make
sure that there is no race conditions or dead locks in your program. No silver
bullet - sorry!
## Should I use the constructor/destructor of the test fixture or the set-up/tear-down function? ##
The first thing to remember is that Google Test does not reuse the
same test fixture object across multiple tests. For each `TEST_F`,
Google Test will create a fresh test fixture object, _immediately_
call `SetUp()`, run the test, call `TearDown()`, and then
_immediately_ delete the test fixture object. Therefore, there is no
need to write a `SetUp()` or `TearDown()` function if the constructor
or destructor already does the job.
You may still want to use `SetUp()/TearDown()` in the following cases:
* If the tear-down operation could throw an exception, you must use `TearDown()` as opposed to the destructor, as throwing in a destructor leads to undefined behavior and usually will kill your program right away. Note that many standard libraries (like STL) may throw when exceptions are enabled in the compiler. Therefore you should prefer `TearDown()` if you want to write portable tests that work with or without exceptions.
* The assertion macros throw an exception when flag `--gtest_throw_on_failure` is specified. Therefore, you shouldn't use Google Test assertions in a destructor if you plan to run your tests with this flag.
* In a constructor or destructor, you cannot make a virtual function call on this object. (You can call a method declared as virtual, but it will be statically bound.) Therefore, if you need to call a method that will be overriden in a derived class, you have to use `SetUp()/TearDown()`.
## The compiler complains "no matching function to call" when I use ASSERT\_PREDn. How do I fix it? ##
If the predicate function you use in `ASSERT_PRED*` or `EXPECT_PRED*` is
overloaded or a template, the compiler will have trouble figuring out which
overloaded version it should use. `ASSERT_PRED_FORMAT*` and
`EXPECT_PRED_FORMAT*` don't have this problem.
If you see this error, you might want to switch to
`(ASSERT|EXPECT)_PRED_FORMAT*`, which will also give you a better failure
message. If, however, that is not an option, you can resolve the problem by
explicitly telling the compiler which version to pick.
For example, suppose you have
```
bool IsPositive(int n) {
return n > 0;
}
bool IsPositive(double x) {
return x > 0;
}
```
you will get a compiler error if you write
```
EXPECT_PRED1(IsPositive, 5);
```
However, this will work:
```
EXPECT_PRED1(*static_cast<bool (*)(int)>*(IsPositive), 5);
```
(The stuff inside the angled brackets for the `static_cast` operator is the
type of the function pointer for the `int`-version of `IsPositive()`.)
As another example, when you have a template function
```
template <typename T>
bool IsNegative(T x) {
return x < 0;
}
```
you can use it in a predicate assertion like this:
```
ASSERT_PRED1(IsNegative*<int>*, -5);
```
Things are more interesting if your template has more than one parameters. The
following won't compile:
```
ASSERT_PRED2(*GreaterThan<int, int>*, 5, 0);
```
as the C++ pre-processor thinks you are giving `ASSERT_PRED2` 4 arguments,
which is one more than expected. The workaround is to wrap the predicate
function in parentheses:
```
ASSERT_PRED2(*(GreaterThan<int, int>)*, 5, 0);
```
## My compiler complains about "ignoring return value" when I call RUN\_ALL\_TESTS(). Why? ##
Some people had been ignoring the return value of `RUN_ALL_TESTS()`. That is,
instead of
```
return RUN_ALL_TESTS();
```
they write
```
RUN_ALL_TESTS();
```
This is wrong and dangerous. A test runner needs to see the return value of
`RUN_ALL_TESTS()` in order to determine if a test has passed. If your `main()`
function ignores it, your test will be considered successful even if it has a
Google Test assertion failure. Very bad.
To help the users avoid this dangerous bug, the implementation of
`RUN_ALL_TESTS()` causes gcc to raise this warning, when the return value is
ignored. If you see this warning, the fix is simple: just make sure its value
is used as the return value of `main()`.
## My compiler complains that a constructor (or destructor) cannot return a value. What's going on? ##
Due to a peculiarity of C++, in order to support the syntax for streaming
messages to an `ASSERT_*`, e.g.
```
ASSERT_EQ(1, Foo()) << "blah blah" << foo;
```
we had to give up using `ASSERT*` and `FAIL*` (but not `EXPECT*` and
`ADD_FAILURE*`) in constructors and destructors. The workaround is to move the
content of your constructor/destructor to a private void member function, or
switch to `EXPECT_*()` if that works. This section in the user's guide explains
it.
## My set-up function is not called. Why? ##
C++ is case-sensitive. It should be spelled as `SetUp()`. Did you
spell it as `Setup()`?
Similarly, sometimes people spell `SetUpTestCase()` as `SetupTestCase()` and
wonder why it's never called.
## How do I jump to the line of a failure in Emacs directly? ##
Google Test's failure message format is understood by Emacs and many other
IDEs, like acme and XCode. If a Google Test message is in a compilation buffer
in Emacs, then it's clickable. You can now hit `enter` on a message to jump to
the corresponding source code, or use `C-x `` to jump to the next failure.
## I have several test cases which share the same test fixture logic, do I have to define a new test fixture class for each of them? This seems pretty tedious. ##
You don't have to. Instead of
```
class FooTest : public BaseTest {};
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
class BarTest : public BaseTest {};
TEST_F(BarTest, Abc) { ... }
TEST_F(BarTest, Def) { ... }
```
you can simply `typedef` the test fixtures:
```
typedef BaseTest FooTest;
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
typedef BaseTest BarTest;
TEST_F(BarTest, Abc) { ... }
TEST_F(BarTest, Def) { ... }
```
## The Google Test output is buried in a whole bunch of log messages. What do I do? ##
The Google Test output is meant to be a concise and human-friendly report. If
your test generates textual output itself, it will mix with the Google Test
output, making it hard to read. However, there is an easy solution to this
problem.
Since most log messages go to stderr, we decided to let Google Test output go
to stdout. This way, you can easily separate the two using redirection. For
example:
```
./my_test > googletest_output.txt
```
## Why should I prefer test fixtures over global variables? ##
There are several good reasons:
1. It's likely your test needs to change the states of its global variables. This makes it difficult to keep side effects from escaping one test and contaminating others, making debugging difficult. By using fixtures, each test has a fresh set of variables that's different (but with the same names). Thus, tests are kept independent of each other.
1. Global variables pollute the global namespace.
1. Test fixtures can be reused via subclassing, which cannot be done easily with global variables. This is useful if many test cases have something in common.
## How do I test private class members without writing FRIEND\_TEST()s? ##
You should try to write testable code, which means classes should be easily
tested from their public interface. One way to achieve this is the Pimpl idiom:
you move all private members of a class into a helper class, and make all
members of the helper class public.
You have several other options that don't require using `FRIEND_TEST`:
* Write the tests as members of the fixture class:
```
class Foo {
friend class FooTest;
...
};
class FooTest : public ::testing::Test {
protected:
...
void Test1() {...} // This accesses private members of class Foo.
void Test2() {...} // So does this one.
};
TEST_F(FooTest, Test1) {
Test1();
}
TEST_F(FooTest, Test2) {
Test2();
}
```
* In the fixture class, write accessors for the tested class' private members, then use the accessors in your tests:
```
class Foo {
friend class FooTest;
...
};
class FooTest : public ::testing::Test {
protected:
...
T1 get_private_member1(Foo* obj) {
return obj->private_member1_;
}
};
TEST_F(FooTest, Test1) {
...
get_private_member1(x)
...
}
```
* If the methods are declared **protected**, you can change their access level in a test-only subclass:
```
class YourClass {
...
protected: // protected access for testability.
int DoSomethingReturningInt();
...
};
// in the your_class_test.cc file:
class TestableYourClass : public YourClass {
...
public: using YourClass::DoSomethingReturningInt; // changes access rights
...
};
TEST_F(YourClassTest, DoSomethingTest) {
TestableYourClass obj;
assertEquals(expected_value, obj.DoSomethingReturningInt());
}
```
## How do I test private class static members without writing FRIEND\_TEST()s? ##
We find private static methods clutter the header file. They are
implementation details and ideally should be kept out of a .h. So often I make
them free functions instead.
Instead of:
```
// foo.h
class Foo {
...
private:
static bool Func(int n);
};
// foo.cc
bool Foo::Func(int n) { ... }
// foo_test.cc
EXPECT_TRUE(Foo::Func(12345));
```
You probably should better write:
```
// foo.h
class Foo {
...
};
// foo.cc
namespace internal {
bool Func(int n) { ... }
}
// foo_test.cc
namespace internal {
bool Func(int n);
}
EXPECT_TRUE(internal::Func(12345));
```
## I would like to run a test several times with different parameters. Do I need to write several similar copies of it? ##
No. You can use a feature called [value-parameterized tests](V1_7_AdvancedGuide.md#Value_Parameterized_Tests) which
lets you repeat your tests with different parameters, without defining it more than once.
## How do I test a file that defines main()? ##
To test a `foo.cc` file, you need to compile and link it into your unit test
program. However, when the file contains a definition for the `main()`
function, it will clash with the `main()` of your unit test, and will result in
a build error.
The right solution is to split it into three files:
1. `foo.h` which contains the declarations,
1. `foo.cc` which contains the definitions except `main()`, and
1. `foo_main.cc` which contains nothing but the definition of `main()`.
Then `foo.cc` can be easily tested.
If you are adding tests to an existing file and don't want an intrusive change
like this, there is a hack: just include the entire `foo.cc` file in your unit
test. For example:
```
// File foo_unittest.cc
// The headers section
...
// Renames main() in foo.cc to make room for the unit test main()
#define main FooMain
#include "a/b/foo.cc"
// The tests start here.
...
```
However, please remember this is a hack and should only be used as the last
resort.
## What can the statement argument in ASSERT\_DEATH() be? ##
`ASSERT_DEATH(_statement_, _regex_)` (or any death assertion macro) can be used
wherever `_statement_` is valid. So basically `_statement_` can be any C++
statement that makes sense in the current context. In particular, it can
reference global and/or local variables, and can be:
* a simple function call (often the case),
* a complex expression, or
* a compound statement.
> Some examples are shown here:
```
// A death test can be a simple function call.
TEST(MyDeathTest, FunctionCall) {
ASSERT_DEATH(Xyz(5), "Xyz failed");
}
// Or a complex expression that references variables and functions.
TEST(MyDeathTest, ComplexExpression) {
const bool c = Condition();
ASSERT_DEATH((c ? Func1(0) : object2.Method("test")),
"(Func1|Method) failed");
}
// Death assertions can be used any where in a function. In
// particular, they can be inside a loop.
TEST(MyDeathTest, InsideLoop) {
// Verifies that Foo(0), Foo(1), ..., and Foo(4) all die.
for (int i = 0; i < 5; i++) {
EXPECT_DEATH_M(Foo(i), "Foo has \\d+ errors",
::testing::Message() << "where i is " << i);
}
}
// A death assertion can contain a compound statement.
TEST(MyDeathTest, CompoundStatement) {
// Verifies that at lease one of Bar(0), Bar(1), ..., and
// Bar(4) dies.
ASSERT_DEATH({
for (int i = 0; i < 5; i++) {
Bar(i);
}
},
"Bar has \\d+ errors");}
```
`googletest_unittest.cc` contains more examples if you are interested.
## What syntax does the regular expression in ASSERT\_DEATH use? ##
On POSIX systems, Google Test uses the POSIX Extended regular
expression syntax
(http://en.wikipedia.org/wiki/Regular_expression#POSIX_Extended_Regular_Expressions).
On Windows, it uses a limited variant of regular expression
syntax. For more details, see the
[regular expression syntax](V1_7_AdvancedGuide.md#Regular_Expression_Syntax).
## I have a fixture class Foo, but TEST\_F(Foo, Bar) gives me error "no matching function for call to Foo::Foo()". Why? ##
Google Test needs to be able to create objects of your test fixture class, so
it must have a default constructor. Normally the compiler will define one for
you. However, there are cases where you have to define your own:
* If you explicitly declare a non-default constructor for class `Foo`, then you need to define a default constructor, even if it would be empty.
* If `Foo` has a const non-static data member, then you have to define the default constructor _and_ initialize the const member in the initializer list of the constructor. (Early versions of `gcc` doesn't force you to initialize the const member. It's a bug that has been fixed in `gcc 4`.)
## Why does ASSERT\_DEATH complain about previous threads that were already joined? ##
With the Linux pthread library, there is no turning back once you cross the
line from single thread to multiple threads. The first time you create a
thread, a manager thread is created in addition, so you get 3, not 2, threads.
Later when the thread you create joins the main thread, the thread count
decrements by 1, but the manager thread will never be killed, so you still have
2 threads, which means you cannot safely run a death test.
The new NPTL thread library doesn't suffer from this problem, as it doesn't
create a manager thread. However, if you don't control which machine your test
runs on, you shouldn't depend on this.
## Why does Google Test require the entire test case, instead of individual tests, to be named FOODeathTest when it uses ASSERT\_DEATH? ##
Google Test does not interleave tests from different test cases. That is, it
runs all tests in one test case first, and then runs all tests in the next test
case, and so on. Google Test does this because it needs to set up a test case
before the first test in it is run, and tear it down afterwords. Splitting up
the test case would require multiple set-up and tear-down processes, which is
inefficient and makes the semantics unclean.
If we were to determine the order of tests based on test name instead of test
case name, then we would have a problem with the following situation:
```
TEST_F(FooTest, AbcDeathTest) { ... }
TEST_F(FooTest, Uvw) { ... }
TEST_F(BarTest, DefDeathTest) { ... }
TEST_F(BarTest, Xyz) { ... }
```
Since `FooTest.AbcDeathTest` needs to run before `BarTest.Xyz`, and we don't
interleave tests from different test cases, we need to run all tests in the
`FooTest` case before running any test in the `BarTest` case. This contradicts
with the requirement to run `BarTest.DefDeathTest` before `FooTest.Uvw`.
## But I don't like calling my entire test case FOODeathTest when it contains both death tests and non-death tests. What do I do? ##
You don't have to, but if you like, you may split up the test case into
`FooTest` and `FooDeathTest`, where the names make it clear that they are
related:
```
class FooTest : public ::testing::Test { ... };
TEST_F(FooTest, Abc) { ... }
TEST_F(FooTest, Def) { ... }
typedef FooTest FooDeathTest;
TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
```
## The compiler complains about "no match for 'operator<<'" when I use an assertion. What gives? ##
If you use a user-defined type `FooType` in an assertion, you must make sure
there is an `std::ostream& operator<<(std::ostream&, const FooType&)` function
defined such that we can print a value of `FooType`.
In addition, if `FooType` is declared in a name space, the `<<` operator also
needs to be defined in the _same_ name space.
## How do I suppress the memory leak messages on Windows? ##
Since the statically initialized Google Test singleton requires allocations on
the heap, the Visual C++ memory leak detector will report memory leaks at the
end of the program run. The easiest way to avoid this is to use the
`_CrtMemCheckpoint` and `_CrtMemDumpAllObjectsSince` calls to not report any
statically initialized heap objects. See MSDN for more details and additional
heap check/debug routines.
## I am building my project with Google Test in Visual Studio and all I'm getting is a bunch of linker errors (or warnings). Help! ##
You may get a number of the following linker error or warnings if you
attempt to link your test project with the Google Test library when
your project and the are not built using the same compiler settings.
* LNK2005: symbol already defined in object
* LNK4217: locally defined symbol 'symbol' imported in function 'function'
* LNK4049: locally defined symbol 'symbol' imported
The Google Test project (gtest.vcproj) has the Runtime Library option
set to /MT (use multi-threaded static libraries, /MTd for debug). If
your project uses something else, for example /MD (use multi-threaded
DLLs, /MDd for debug), you need to change the setting in the Google
Test project to match your project's.
To update this setting open the project properties in the Visual
Studio IDE then select the branch Configuration Properties | C/C++ |
Code Generation and change the option "Runtime Library". You may also try
using gtest-md.vcproj instead of gtest.vcproj.
## I put my tests in a library and Google Test doesn't run them. What's happening? ##
Have you read a
[warning](V1_7_Primer.md#important-note-for-visual-c-users) on
the Google Test Primer page?
## I want to use Google Test with Visual Studio but don't know where to start. ##
Many people are in your position and one of the posted his solution to
our mailing list. Here is his link:
http://hassanjamilahmad.blogspot.com/2009/07/gtest-starters-help.html.
## I am seeing compile errors mentioning std::type\_traits when I try to use Google Test on Solaris. ##
Google Test uses parts of the standard C++ library that SunStudio does not support.
Our users reported success using alternative implementations. Try running the build after runing this commad:
`export CC=cc CXX=CC CXXFLAGS='-library=stlport4'`
## How can my code detect if it is running in a test? ##
If you write code that sniffs whether it's running in a test and does
different things accordingly, you are leaking test-only logic into
production code and there is no easy way to ensure that the test-only
code paths aren't run by mistake in production. Such cleverness also
leads to
[Heisenbugs](http://en.wikipedia.org/wiki/Unusual_software_bug#Heisenbug).
Therefore we strongly advise against the practice, and Google Test doesn't
provide a way to do it.
In general, the recommended way to cause the code to behave
differently under test is [dependency injection](http://jamesshore.com/Blog/Dependency-Injection-Demystified.html).
You can inject different functionality from the test and from the
production code. Since your production code doesn't link in the
for-test logic at all, there is no danger in accidentally running it.
However, if you _really_, _really_, _really_ have no choice, and if
you follow the rule of ending your test program names with `_test`,
you can use the _horrible_ hack of sniffing your executable name
(`argv[0]` in `main()`) to know whether the code is under test.
## Google Test defines a macro that clashes with one defined by another library. How do I deal with that? ##
In C++, macros don't obey namespaces. Therefore two libraries that
both define a macro of the same name will clash if you `#include` both
definitions. In case a Google Test macro clashes with another
library, you can force Google Test to rename its macro to avoid the
conflict.
Specifically, if both Google Test and some other code define macro
`FOO`, you can add
```
-DGTEST_DONT_DEFINE_FOO=1
```
to the compiler flags to tell Google Test to change the macro's name
from `FOO` to `GTEST_FOO`. For example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll need to write
```
GTEST_TEST(SomeTest, DoesThis) { ... }
```
instead of
```
TEST(SomeTest, DoesThis) { ... }
```
in order to define a test.
Currently, the following `TEST`, `FAIL`, `SUCCEED`, and the basic comparison assertion macros can have alternative names. You can see the full list of covered macros [here](http://www.google.com/codesearch?q=if+!GTEST_DONT_DEFINE_\w%2B+package:http://googletest\.googlecode\.com+file:/include/gtest/gtest.h). More information can be found in the "Avoiding Macro Name Clashes" section of the README file.
## Is it OK if I have two separate `TEST(Foo, Bar)` test methods defined in different namespaces? ##
Yes.
The rule is **all test methods in the same test case must use the same fixture class**. This means that the following is **allowed** because both tests use the same fixture class (`::testing::Test`).
```
namespace foo {
TEST(CoolTest, DoSomething) {
SUCCEED();
}
} // namespace foo
namespace bar {
TEST(CoolTest, DoSomething) {
SUCCEED();
}
} // namespace foo
```
However, the following code is **not allowed** and will produce a runtime error from Google Test because the test methods are using different test fixture classes with the same test case name.
```
namespace foo {
class CoolTest : public ::testing::Test {}; // Fixture foo::CoolTest
TEST_F(CoolTest, DoSomething) {
SUCCEED();
}
} // namespace foo
namespace bar {
class CoolTest : public ::testing::Test {}; // Fixture: bar::CoolTest
TEST_F(CoolTest, DoSomething) {
SUCCEED();
}
} // namespace foo
```
## How do I build Google Testing Framework with Xcode 4? ##
If you try to build Google Test's Xcode project with Xcode 4.0 or later, you may encounter an error message that looks like
"Missing SDK in target gtest\_framework: /Developer/SDKs/MacOSX10.4u.sdk". That means that Xcode does not support the SDK the project is targeting. See the Xcode section in the [README](../../README.MD) file on how to resolve this.
## My question is not covered in your FAQ! ##
If you cannot find the answer to your question in this FAQ, there are
some other resources you can use:
1. read other [wiki pages](http://code.google.com/p/googletest/w/list),
1. search the mailing list [archive](http://groups.google.com/group/googletestframework/topics),
1. ask it on [googletestframework@googlegroups.com](mailto:googletestframework@googlegroups.com) and someone will answer it (to prevent spam, we require you to join the [discussion group](http://groups.google.com/group/googletestframework) before you can post.).
Please note that creating an issue in the
[issue tracker](http://code.google.com/p/googletest/issues/list) is _not_
a good way to get your answer, as it is monitored infrequently by a
very small number of people.
When asking a question, it's helpful to provide as much of the
following information as possible (people cannot help you if there's
not enough information in your question):
* the version (or the revision number if you check out from SVN directly) of Google Test you use (Google Test is under active development, so it's possible that your problem has been solved in a later version),
* your operating system,
* the name and version of your compiler,
* the complete command line flags you give to your compiler,
* the complete compiler error messages (if the question is about compilation),
* the _actual_ code (ideally, a minimal but complete program) that has the problem you encounter.
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# Introduction: Why Google C++ Testing Framework? #
_Google C++ Testing Framework_ helps you write better C++ tests.
No matter whether you work on Linux, Windows, or a Mac, if you write C++ code,
Google Test can help you.
So what makes a good test, and how does Google C++ Testing Framework fit in? We believe:
1. Tests should be _independent_ and _repeatable_. It's a pain to debug a test that succeeds or fails as a result of other tests. Google C++ Testing Framework isolates the tests by running each of them on a different object. When a test fails, Google C++ Testing Framework allows you to run it in isolation for quick debugging.
1. Tests should be well _organized_ and reflect the structure of the tested code. Google C++ Testing Framework groups related tests into test cases that can share data and subroutines. This common pattern is easy to recognize and makes tests easy to maintain. Such consistency is especially helpful when people switch projects and start to work on a new code base.
1. Tests should be _portable_ and _reusable_. The open-source community has a lot of code that is platform-neutral, its tests should also be platform-neutral. Google C++ Testing Framework works on different OSes, with different compilers (gcc, MSVC, and others), with or without exceptions, so Google C++ Testing Framework tests can easily work with a variety of configurations. (Note that the current release only contains build scripts for Linux - we are actively working on scripts for other platforms.)
1. When tests fail, they should provide as much _information_ about the problem as possible. Google C++ Testing Framework doesn't stop at the first test failure. Instead, it only stops the current test and continues with the next. You can also set up tests that report non-fatal failures after which the current test continues. Thus, you can detect and fix multiple bugs in a single run-edit-compile cycle.
1. The testing framework should liberate test writers from housekeeping chores and let them focus on the test _content_. Google C++ Testing Framework automatically keeps track of all tests defined, and doesn't require the user to enumerate them in order to run them.
1. Tests should be _fast_. With Google C++ Testing Framework, you can reuse shared resources across tests and pay for the set-up/tear-down only once, without making tests depend on each other.
Since Google C++ Testing Framework is based on the popular xUnit
architecture, you'll feel right at home if you've used JUnit or PyUnit before.
If not, it will take you about 10 minutes to learn the basics and get started.
So let's go!
_Note:_ We sometimes refer to Google C++ Testing Framework informally
as _Google Test_.
# Setting up a New Test Project #
To write a test program using Google Test, you need to compile Google
Test into a library and link your test with it. We provide build
files for some popular build systems: `msvc/` for Visual Studio,
`xcode/` for Mac Xcode, `make/` for GNU make, `codegear/` for Borland
C++ Builder, and the autotools script (deprecated) and
`CMakeLists.txt` for CMake (recommended) in the Google Test root
directory. If your build system is not on this list, you can take a
look at `make/Makefile` to learn how Google Test should be compiled
(basically you want to compile `src/gtest-all.cc` with `GTEST_ROOT`
and `GTEST_ROOT/include` in the header search path, where `GTEST_ROOT`
is the Google Test root directory).
Once you are able to compile the Google Test library, you should
create a project or build target for your test program. Make sure you
have `GTEST_ROOT/include` in the header search path so that the
compiler can find `"gtest/gtest.h"` when compiling your test. Set up
your test project to link with the Google Test library (for example,
in Visual Studio, this is done by adding a dependency on
`gtest.vcproj`).
If you still have questions, take a look at how Google Test's own
tests are built and use them as examples.
# Basic Concepts #
When using Google Test, you start by writing _assertions_, which are statements
that check whether a condition is true. An assertion's result can be _success_,
_nonfatal failure_, or _fatal failure_. If a fatal failure occurs, it aborts
the current function; otherwise the program continues normally.
_Tests_ use assertions to verify the tested code's behavior. If a test crashes
or has a failed assertion, then it _fails_; otherwise it _succeeds_.
A _test case_ contains one or many tests. You should group your tests into test
cases that reflect the structure of the tested code. When multiple tests in a
test case need to share common objects and subroutines, you can put them into a
_test fixture_ class.
A _test program_ can contain multiple test cases.
We'll now explain how to write a test program, starting at the individual
assertion level and building up to tests and test cases.
# Assertions #
Google Test assertions are macros that resemble function calls. You test a
class or function by making assertions about its behavior. When an assertion
fails, Google Test prints the assertion's source file and line number location,
along with a failure message. You may also supply a custom failure message
which will be appended to Google Test's message.
The assertions come in pairs that test the same thing but have different
effects on the current function. `ASSERT_*` versions generate fatal failures
when they fail, and **abort the current function**. `EXPECT_*` versions generate
nonfatal failures, which don't abort the current function. Usually `EXPECT_*`
are preferred, as they allow more than one failures to be reported in a test.
However, you should use `ASSERT_*` if it doesn't make sense to continue when
the assertion in question fails.
Since a failed `ASSERT_*` returns from the current function immediately,
possibly skipping clean-up code that comes after it, it may cause a space leak.
Depending on the nature of the leak, it may or may not be worth fixing - so
keep this in mind if you get a heap checker error in addition to assertion
errors.
To provide a custom failure message, simply stream it into the macro using the
`<<` operator, or a sequence of such operators. An example:
```
ASSERT_EQ(x.size(), y.size()) << "Vectors x and y are of unequal length";
for (int i = 0; i < x.size(); ++i) {
EXPECT_EQ(x[i], y[i]) << "Vectors x and y differ at index " << i;
}
```
Anything that can be streamed to an `ostream` can be streamed to an assertion
macro--in particular, C strings and `string` objects. If a wide string
(`wchar_t*`, `TCHAR*` in `UNICODE` mode on Windows, or `std::wstring`) is
streamed to an assertion, it will be translated to UTF-8 when printed.
## Basic Assertions ##
These assertions do basic true/false condition testing.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_TRUE(`_condition_`)`; | `EXPECT_TRUE(`_condition_`)`; | _condition_ is true |
| `ASSERT_FALSE(`_condition_`)`; | `EXPECT_FALSE(`_condition_`)`; | _condition_ is false |
Remember, when they fail, `ASSERT_*` yields a fatal failure and
returns from the current function, while `EXPECT_*` yields a nonfatal
failure, allowing the function to continue running. In either case, an
assertion failure means its containing test fails.
_Availability_: Linux, Windows, Mac.
## Binary Comparison ##
This section describes assertions that compare two values.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
|`ASSERT_EQ(`_expected_`, `_actual_`);`|`EXPECT_EQ(`_expected_`, `_actual_`);`| _expected_ `==` _actual_ |
|`ASSERT_NE(`_val1_`, `_val2_`);` |`EXPECT_NE(`_val1_`, `_val2_`);` | _val1_ `!=` _val2_ |
|`ASSERT_LT(`_val1_`, `_val2_`);` |`EXPECT_LT(`_val1_`, `_val2_`);` | _val1_ `<` _val2_ |
|`ASSERT_LE(`_val1_`, `_val2_`);` |`EXPECT_LE(`_val1_`, `_val2_`);` | _val1_ `<=` _val2_ |
|`ASSERT_GT(`_val1_`, `_val2_`);` |`EXPECT_GT(`_val1_`, `_val2_`);` | _val1_ `>` _val2_ |
|`ASSERT_GE(`_val1_`, `_val2_`);` |`EXPECT_GE(`_val1_`, `_val2_`);` | _val1_ `>=` _val2_ |
In the event of a failure, Google Test prints both _val1_ and _val2_
. In `ASSERT_EQ*` and `EXPECT_EQ*` (and all other equality assertions
we'll introduce later), you should put the expression you want to test
in the position of _actual_, and put its expected value in _expected_,
as Google Test's failure messages are optimized for this convention.
Value arguments must be comparable by the assertion's comparison
operator or you'll get a compiler error. We used to require the
arguments to support the `<<` operator for streaming to an `ostream`,
but it's no longer necessary since v1.6.0 (if `<<` is supported, it
will be called to print the arguments when the assertion fails;
otherwise Google Test will attempt to print them in the best way it
can. For more details and how to customize the printing of the
arguments, see this Google Mock [recipe](../../googlemock/docs/CookBook.md#teaching-google-mock-how-to-print-your-values).).
These assertions can work with a user-defined type, but only if you define the
corresponding comparison operator (e.g. `==`, `<`, etc). If the corresponding
operator is defined, prefer using the `ASSERT_*()` macros because they will
print out not only the result of the comparison, but the two operands as well.
Arguments are always evaluated exactly once. Therefore, it's OK for the
arguments to have side effects. However, as with any ordinary C/C++ function,
the arguments' evaluation order is undefined (i.e. the compiler is free to
choose any order) and your code should not depend on any particular argument
evaluation order.
`ASSERT_EQ()` does pointer equality on pointers. If used on two C strings, it
tests if they are in the same memory location, not if they have the same value.
Therefore, if you want to compare C strings (e.g. `const char*`) by value, use
`ASSERT_STREQ()` , which will be described later on. In particular, to assert
that a C string is `NULL`, use `ASSERT_STREQ(NULL, c_string)` . However, to
compare two `string` objects, you should use `ASSERT_EQ`.
Macros in this section work with both narrow and wide string objects (`string`
and `wstring`).
_Availability_: Linux, Windows, Mac.
## String Comparison ##
The assertions in this group compare two **C strings**. If you want to compare
two `string` objects, use `EXPECT_EQ`, `EXPECT_NE`, and etc instead.
| **Fatal assertion** | **Nonfatal assertion** | **Verifies** |
|:--------------------|:-----------------------|:-------------|
| `ASSERT_STREQ(`_expected\_str_`, `_actual\_str_`);` | `EXPECT_STREQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content |
| `ASSERT_STRNE(`_str1_`, `_str2_`);` | `EXPECT_STRNE(`_str1_`, `_str2_`);` | the two C strings have different content |
| `ASSERT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);`| `EXPECT_STRCASEEQ(`_expected\_str_`, `_actual\_str_`);` | the two C strings have the same content, ignoring case |
| `ASSERT_STRCASENE(`_str1_`, `_str2_`);`| `EXPECT_STRCASENE(`_str1_`, `_str2_`);` | the two C strings have different content, ignoring case |
Note that "CASE" in an assertion name means that case is ignored.
`*STREQ*` and `*STRNE*` also accept wide C strings (`wchar_t*`). If a
comparison of two wide strings fails, their values will be printed as UTF-8
narrow strings.
A `NULL` pointer and an empty string are considered _different_.
_Availability_: Linux, Windows, Mac.
See also: For more string comparison tricks (substring, prefix, suffix, and
regular expression matching, for example), see the [Advanced Google Test Guide](V1_7_AdvancedGuide.md).
# Simple Tests #
To create a test:
1. Use the `TEST()` macro to define and name a test function, These are ordinary C++ functions that don't return a value.
1. In this function, along with any valid C++ statements you want to include, use the various Google Test assertions to check values.
1. The test's result is determined by the assertions; if any assertion in the test fails (either fatally or non-fatally), or if the test crashes, the entire test fails. Otherwise, it succeeds.
```
TEST(test_case_name, test_name) {
... test body ...
}
```
`TEST()` arguments go from general to specific. The _first_ argument is the
name of the test case, and the _second_ argument is the test's name within the
test case. Both names must be valid C++ identifiers, and they should not contain underscore (`_`). A test's _full name_ consists of its containing test case and its
individual name. Tests from different test cases can have the same individual
name.
For example, let's take a simple integer function:
```
int Factorial(int n); // Returns the factorial of n
```
A test case for this function might look like:
```
// Tests factorial of 0.
TEST(FactorialTest, HandlesZeroInput) {
EXPECT_EQ(1, Factorial(0));
}
// Tests factorial of positive numbers.
TEST(FactorialTest, HandlesPositiveInput) {
EXPECT_EQ(1, Factorial(1));
EXPECT_EQ(2, Factorial(2));
EXPECT_EQ(6, Factorial(3));
EXPECT_EQ(40320, Factorial(8));
}
```
Google Test groups the test results by test cases, so logically-related tests
should be in the same test case; in other words, the first argument to their
`TEST()` should be the same. In the above example, we have two tests,
`HandlesZeroInput` and `HandlesPositiveInput`, that belong to the same test
case `FactorialTest`.
_Availability_: Linux, Windows, Mac.
# Test Fixtures: Using the Same Data Configuration for Multiple Tests #
If you find yourself writing two or more tests that operate on similar data,
you can use a _test fixture_. It allows you to reuse the same configuration of
objects for several different tests.
To create a fixture, just:
1. Derive a class from `::testing::Test` . Start its body with `protected:` or `public:` as we'll want to access fixture members from sub-classes.
1. Inside the class, declare any objects you plan to use.
1. If necessary, write a default constructor or `SetUp()` function to prepare the objects for each test. A common mistake is to spell `SetUp()` as `Setup()` with a small `u` - don't let that happen to you.
1. If necessary, write a destructor or `TearDown()` function to release any resources you allocated in `SetUp()` . To learn when you should use the constructor/destructor and when you should use `SetUp()/TearDown()`, read this [FAQ entry](V1_7_FAQ.md#should-i-use-the-constructordestructor-of-the-test-fixture-or-the-set-uptear-down-function).
1. If needed, define subroutines for your tests to share.
When using a fixture, use `TEST_F()` instead of `TEST()` as it allows you to
access objects and subroutines in the test fixture:
```
TEST_F(test_case_name, test_name) {
... test body ...
}
```
Like `TEST()`, the first argument is the test case name, but for `TEST_F()`
this must be the name of the test fixture class. You've probably guessed: `_F`
is for fixture.
Unfortunately, the C++ macro system does not allow us to create a single macro
that can handle both types of tests. Using the wrong macro causes a compiler
error.
Also, you must first define a test fixture class before using it in a
`TEST_F()`, or you'll get the compiler error "`virtual outside class
declaration`".
For each test defined with `TEST_F()`, Google Test will:
1. Create a _fresh_ test fixture at runtime
1. Immediately initialize it via `SetUp()` ,
1. Run the test
1. Clean up by calling `TearDown()`
1. Delete the test fixture. Note that different tests in the same test case have different test fixture objects, and Google Test always deletes a test fixture before it creates the next one. Google Test does not reuse the same test fixture for multiple tests. Any changes one test makes to the fixture do not affect other tests.
As an example, let's write tests for a FIFO queue class named `Queue`, which
has the following interface:
```
template <typename E> // E is the element type.
class Queue {
public:
Queue();
void Enqueue(const E& element);
E* Dequeue(); // Returns NULL if the queue is empty.
size_t size() const;
...
};
```
First, define a fixture class. By convention, you should give it the name
`FooTest` where `Foo` is the class being tested.
```
class QueueTest : public ::testing::Test {
protected:
virtual void SetUp() {
q1_.Enqueue(1);
q2_.Enqueue(2);
q2_.Enqueue(3);
}
// virtual void TearDown() {}
Queue<int> q0_;
Queue<int> q1_;
Queue<int> q2_;
};
```
In this case, `TearDown()` is not needed since we don't have to clean up after
each test, other than what's already done by the destructor.
Now we'll write tests using `TEST_F()` and this fixture.
```
TEST_F(QueueTest, IsEmptyInitially) {
EXPECT_EQ(0, q0_.size());
}
TEST_F(QueueTest, DequeueWorks) {
int* n = q0_.Dequeue();
EXPECT_EQ(NULL, n);
n = q1_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(1, *n);
EXPECT_EQ(0, q1_.size());
delete n;
n = q2_.Dequeue();
ASSERT_TRUE(n != NULL);
EXPECT_EQ(2, *n);
EXPECT_EQ(1, q2_.size());
delete n;
}
```
The above uses both `ASSERT_*` and `EXPECT_*` assertions. The rule of thumb is
to use `EXPECT_*` when you want the test to continue to reveal more errors
after the assertion failure, and use `ASSERT_*` when continuing after failure
doesn't make sense. For example, the second assertion in the `Dequeue` test is
`ASSERT_TRUE(n != NULL)`, as we need to dereference the pointer `n` later,
which would lead to a segfault when `n` is `NULL`.
When these tests run, the following happens:
1. Google Test constructs a `QueueTest` object (let's call it `t1` ).
1. `t1.SetUp()` initializes `t1` .
1. The first test ( `IsEmptyInitially` ) runs on `t1` .
1. `t1.TearDown()` cleans up after the test finishes.
1. `t1` is destructed.
1. The above steps are repeated on another `QueueTest` object, this time running the `DequeueWorks` test.
_Availability_: Linux, Windows, Mac.
_Note_: Google Test automatically saves all _Google Test_ flags when a test
object is constructed, and restores them when it is destructed.
# Invoking the Tests #
`TEST()` and `TEST_F()` implicitly register their tests with Google Test. So, unlike with many other C++ testing frameworks, you don't have to re-list all your defined tests in order to run them.
After defining your tests, you can run them with `RUN_ALL_TESTS()` , which returns `0` if all the tests are successful, or `1` otherwise. Note that `RUN_ALL_TESTS()` runs _all tests_ in your link unit -- they can be from different test cases, or even different source files.
When invoked, the `RUN_ALL_TESTS()` macro:
1. Saves the state of all Google Test flags.
1. Creates a test fixture object for the first test.
1. Initializes it via `SetUp()`.
1. Runs the test on the fixture object.
1. Cleans up the fixture via `TearDown()`.
1. Deletes the fixture.
1. Restores the state of all Google Test flags.
1. Repeats the above steps for the next test, until all tests have run.
In addition, if the text fixture's constructor generates a fatal failure in
step 2, there is no point for step 3 - 5 and they are thus skipped. Similarly,
if step 3 generates a fatal failure, step 4 will be skipped.
_Important_: You must not ignore the return value of `RUN_ALL_TESTS()`, or `gcc`
will give you a compiler error. The rationale for this design is that the
automated testing service determines whether a test has passed based on its
exit code, not on its stdout/stderr output; thus your `main()` function must
return the value of `RUN_ALL_TESTS()`.
Also, you should call `RUN_ALL_TESTS()` only **once**. Calling it more than once
conflicts with some advanced Google Test features (e.g. thread-safe death
tests) and thus is not supported.
_Availability_: Linux, Windows, Mac.
# Writing the main() Function #
You can start from this boilerplate:
```
#include "this/package/foo.h"
#include "gtest/gtest.h"
namespace {
// The fixture for testing class Foo.
class FooTest : public ::testing::Test {
protected:
// You can remove any or all of the following functions if its body
// is empty.
FooTest() {
// You can do set-up work for each test here.
}
virtual ~FooTest() {
// You can do clean-up work that doesn't throw exceptions here.
}
// If the constructor and destructor are not enough for setting up
// and cleaning up each test, you can define the following methods:
virtual void SetUp() {
// Code here will be called immediately after the constructor (right
// before each test).
}
virtual void TearDown() {
// Code here will be called immediately after each test (right
// before the destructor).
}
// Objects declared here can be used by all tests in the test case for Foo.
};
// Tests that the Foo::Bar() method does Abc.
TEST_F(FooTest, MethodBarDoesAbc) {
const string input_filepath = "this/package/testdata/myinputfile.dat";
const string output_filepath = "this/package/testdata/myoutputfile.dat";
Foo f;
EXPECT_EQ(0, f.Bar(input_filepath, output_filepath));
}
// Tests that Foo does Xyz.
TEST_F(FooTest, DoesXyz) {
// Exercises the Xyz feature of Foo.
}
} // namespace
int main(int argc, char **argv) {
::testing::InitGoogleTest(&argc, argv);
return RUN_ALL_TESTS();
}
```
The `::testing::InitGoogleTest()` function parses the command line for Google
Test flags, and removes all recognized flags. This allows the user to control a
test program's behavior via various flags, which we'll cover in [AdvancedGuide](V1_7_AdvancedGuide.md).
You must call this function before calling `RUN_ALL_TESTS()`, or the flags
won't be properly initialized.
On Windows, `InitGoogleTest()` also works with wide strings, so it can be used
in programs compiled in `UNICODE` mode as well.
But maybe you think that writing all those main() functions is too much work? We agree with you completely and that's why Google Test provides a basic implementation of main(). If it fits your needs, then just link your test with gtest\_main library and you are good to go.
## Important note for Visual C++ users ##
If you put your tests into a library and your `main()` function is in a different library or in your .exe file, those tests will not run. The reason is a [bug](https://connect.microsoft.com/feedback/viewfeedback.aspx?FeedbackID=244410&siteid=210) in Visual C++. When you define your tests, Google Test creates certain static objects to register them. These objects are not referenced from elsewhere but their constructors are still supposed to run. When Visual C++ linker sees that nothing in the library is referenced from other places it throws the library out. You have to reference your library with tests from your main program to keep the linker from discarding it. Here is how to do it. Somewhere in your library code declare a function:
```
__declspec(dllexport) int PullInMyLibrary() { return 0; }
```
If you put your tests in a static library (not DLL) then `__declspec(dllexport)` is not required. Now, in your main program, write a code that invokes that function:
```
int PullInMyLibrary();
static int dummy = PullInMyLibrary();
```
This will keep your tests referenced and will make them register themselves at startup.
In addition, if you define your tests in a static library, add `/OPT:NOREF` to your main program linker options. If you use MSVC++ IDE, go to your .exe project properties/Configuration Properties/Linker/Optimization and set References setting to `Keep Unreferenced Data (/OPT:NOREF)`. This will keep Visual C++ linker from discarding individual symbols generated by your tests from the final executable.
There is one more pitfall, though. If you use Google Test as a static library (that's how it is defined in gtest.vcproj) your tests must also reside in a static library. If you have to have them in a DLL, you _must_ change Google Test to build into a DLL as well. Otherwise your tests will not run correctly or will not run at all. The general conclusion here is: make your life easier - do not write your tests in libraries!
# Where to Go from Here #
Congratulations! You've learned the Google Test basics. You can start writing
and running Google Test tests, read some [samples](V1_7_Samples.md), or continue with
[AdvancedGuide](V1_7_AdvancedGuide.md), which describes many more useful Google Test features.
# Known Limitations #
Google Test is designed to be thread-safe. The implementation is
thread-safe on systems where the `pthreads` library is available. It
is currently _unsafe_ to use Google Test assertions from two threads
concurrently on other systems (e.g. Windows). In most tests this is
not an issue as usually the assertions are done in the main thread. If
you want to help, you can volunteer to implement the necessary
synchronization primitives in `gtest-port.h` for your platform.
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<b>P</b>ump is <b>U</b>seful for <b>M</b>eta <b>P</b>rogramming.
# The Problem #
Template and macro libraries often need to define many classes,
functions, or macros that vary only (or almost only) in the number of
arguments they take. It's a lot of repetitive, mechanical, and
error-prone work.
Variadic templates and variadic macros can alleviate the problem.
However, while both are being considered by the C++ committee, neither
is in the standard yet or widely supported by compilers. Thus they
are often not a good choice, especially when your code needs to be
portable. And their capabilities are still limited.
As a result, authors of such libraries often have to write scripts to
generate their implementation. However, our experience is that it's
tedious to write such scripts, which tend to reflect the structure of
the generated code poorly and are often hard to read and edit. For
example, a small change needed in the generated code may require some
non-intuitive, non-trivial changes in the script. This is especially
painful when experimenting with the code.
# Our Solution #
Pump (for Pump is Useful for Meta Programming, Pretty Useful for Meta
Programming, or Practical Utility for Meta Programming, whichever you
prefer) is a simple meta-programming tool for C++. The idea is that a
programmer writes a `foo.pump` file which contains C++ code plus meta
code that manipulates the C++ code. The meta code can handle
iterations over a range, nested iterations, local meta variable
definitions, simple arithmetic, and conditional expressions. You can
view it as a small Domain-Specific Language. The meta language is
designed to be non-intrusive (s.t. it won't confuse Emacs' C++ mode,
for example) and concise, making Pump code intuitive and easy to
maintain.
## Highlights ##
* The implementation is in a single Python script and thus ultra portable: no build or installation is needed and it works cross platforms.
* Pump tries to be smart with respect to [Google's style guide](http://code.google.com/p/google-styleguide/): it breaks long lines (easy to have when they are generated) at acceptable places to fit within 80 columns and indent the continuation lines correctly.
* The format is human-readable and more concise than XML.
* The format works relatively well with Emacs' C++ mode.
## Examples ##
The following Pump code (where meta keywords start with `$`, `[[` and `]]` are meta brackets, and `$$` starts a meta comment that ends with the line):
```
$var n = 3 $$ Defines a meta variable n.
$range i 0..n $$ Declares the range of meta iterator i (inclusive).
$for i [[
$$ Meta loop.
// Foo$i does blah for $i-ary predicates.
$range j 1..i
template <size_t N $for j [[, typename A$j]]>
class Foo$i {
$if i == 0 [[
blah a;
]] $elif i <= 2 [[
blah b;
]] $else [[
blah c;
]]
};
]]
```
will be translated by the Pump compiler to:
```
// Foo0 does blah for 0-ary predicates.
template <size_t N>
class Foo0 {
blah a;
};
// Foo1 does blah for 1-ary predicates.
template <size_t N, typename A1>
class Foo1 {
blah b;
};
// Foo2 does blah for 2-ary predicates.
template <size_t N, typename A1, typename A2>
class Foo2 {
blah b;
};
// Foo3 does blah for 3-ary predicates.
template <size_t N, typename A1, typename A2, typename A3>
class Foo3 {
blah c;
};
```
In another example,
```
$range i 1..n
Func($for i + [[a$i]]);
$$ The text between i and [[ is the separator between iterations.
```
will generate one of the following lines (without the comments), depending on the value of `n`:
```
Func(); // If n is 0.
Func(a1); // If n is 1.
Func(a1 + a2); // If n is 2.
Func(a1 + a2 + a3); // If n is 3.
// And so on...
```
## Constructs ##
We support the following meta programming constructs:
| `$var id = exp` | Defines a named constant value. `$id` is valid util the end of the current meta lexical block. |
|:----------------|:-----------------------------------------------------------------------------------------------|
| `$range id exp..exp` | Sets the range of an iteration variable, which can be reused in multiple loops later. |
| `$for id sep [[ code ]]` | Iteration. The range of `id` must have been defined earlier. `$id` is valid in `code`. |
| `$($)` | Generates a single `$` character. |
| `$id` | Value of the named constant or iteration variable. |
| `$(exp)` | Value of the expression. |
| `$if exp [[ code ]] else_branch` | Conditional. |
| `[[ code ]]` | Meta lexical block. |
| `cpp_code` | Raw C++ code. |
| `$$ comment` | Meta comment. |
**Note:** To give the user some freedom in formatting the Pump source
code, Pump ignores a new-line character if it's right after `$for foo`
or next to `[[` or `]]`. Without this rule you'll often be forced to write
very long lines to get the desired output. Therefore sometimes you may
need to insert an extra new-line in such places for a new-line to show
up in your output.
## Grammar ##
```
code ::= atomic_code*
atomic_code ::= $var id = exp
| $var id = [[ code ]]
| $range id exp..exp
| $for id sep [[ code ]]
| $($)
| $id
| $(exp)
| $if exp [[ code ]] else_branch
| [[ code ]]
| cpp_code
sep ::= cpp_code | empty_string
else_branch ::= $else [[ code ]]
| $elif exp [[ code ]] else_branch
| empty_string
exp ::= simple_expression_in_Python_syntax
```
## Code ##
You can find the source code of Pump in [scripts/pump.py](../scripts/pump.py). It is still
very unpolished and lacks automated tests, although it has been
successfully used many times. If you find a chance to use it in your
project, please let us know what you think! We also welcome help on
improving Pump.
## Real Examples ##
You can find real-world applications of Pump in [Google Test](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgoogletest\.googlecode\.com) and [Google Mock](http://www.google.com/codesearch?q=file%3A\.pump%24+package%3Ahttp%3A%2F%2Fgooglemock\.googlecode\.com). The source file `foo.h.pump` generates `foo.h`.
## Tips ##
* If a meta variable is followed by a letter or digit, you can separate them using `[[]]`, which inserts an empty string. For example `Foo$j[[]]Helper` generate `Foo1Helper` when `j` is 1.
* To avoid extra-long Pump source lines, you can break a line anywhere you want by inserting `[[]]` followed by a new line. Since any new-line character next to `[[` or `]]` is ignored, the generated code won't contain this new line.
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If you're like us, you'd like to look at some Google Test sample code. The
[samples folder](../samples) has a number of well-commented samples showing how to use a
variety of Google Test features.
* [Sample #1](../samples/sample1_unittest.cc) shows the basic steps of using Google Test to test C++ functions.
* [Sample #2](../samples/sample2_unittest.cc) shows a more complex unit test for a class with multiple member functions.
* [Sample #3](../samples/sample3_unittest.cc) uses a test fixture.
* [Sample #4](../samples/sample4_unittest.cc) is another basic example of using Google Test.
* [Sample #5](../samples/sample5_unittest.cc) teaches how to reuse a test fixture in multiple test cases by deriving sub-fixtures from it.
* [Sample #6](../samples/sample6_unittest.cc) demonstrates type-parameterized tests.
* [Sample #7](../samples/sample7_unittest.cc) teaches the basics of value-parameterized tests.
* [Sample #8](../samples/sample8_unittest.cc) shows using `Combine()` in value-parameterized tests.
* [Sample #9](../samples/sample9_unittest.cc) shows use of the listener API to modify Google Test's console output and the use of its reflection API to inspect test results.
* [Sample #10](../samples/sample10_unittest.cc) shows use of the listener API to implement a primitive memory leak checker.
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This guide will explain how to use the Google Testing Framework in your Xcode projects on Mac OS X. This tutorial begins by quickly explaining what to do for experienced users. After the quick start, the guide goes provides additional explanation about each step.
# Quick Start #
Here is the quick guide for using Google Test in your Xcode project.
1. Download the source from the [website](http://code.google.com/p/googletest) using this command: `svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only`
1. Open up the `gtest.xcodeproj` in the `googletest-read-only/xcode/` directory and build the gtest.framework.
1. Create a new "Shell Tool" target in your Xcode project called something like "UnitTests"
1. Add the gtest.framework to your project and add it to the "Link Binary with Libraries" build phase of "UnitTests"
1. Add your unit test source code to the "Compile Sources" build phase of "UnitTests"
1. Edit the "UnitTests" executable and add an environment variable named "DYLD\_FRAMEWORK\_PATH" with a value equal to the path to the framework containing the gtest.framework relative to the compiled executable.
1. Build and Go
The following sections further explain each of the steps listed above in depth, describing in more detail how to complete it including some variations.
# Get the Source #
Currently, the gtest.framework discussed here isn't available in a tagged release of Google Test, it is only available in the trunk. As explained at the Google Test [site](http://code.google.com/p/googletest/source/checkout">svn), you can get the code from anonymous SVN with this command:
```
svn checkout http://googletest.googlecode.com/svn/trunk/ googletest-read-only
```
Alternatively, if you are working with Subversion in your own code base, you can add Google Test as an external dependency to your own Subversion repository. By following this approach, everyone that checks out your svn repository will also receive a copy of Google Test (a specific version, if you wish) without having to check it out explicitly. This makes the set up of your project simpler and reduces the copied code in the repository.
To use `svn:externals`, decide where you would like to have the external source reside. You might choose to put the external source inside the trunk, because you want it to be part of the branch when you make a release. However, keeping it outside the trunk in a version-tagged directory called something like `third-party/googletest/1.0.1`, is another option. Once the location is established, use `svn propedit svn:externals _directory_` to set the svn:externals property on a directory in your repository. This directory won't contain the code, but be its versioned parent directory.
The command `svn propedit` will bring up your Subversion editor, making editing the long, (potentially multi-line) property simpler. This same method can be used to check out a tagged branch, by using the appropriate URL (e.g. `http://googletest.googlecode.com/svn/tags/release-1.0.1`). Additionally, the svn:externals property allows the specification of a particular revision of the trunk with the `-r_##_` option (e.g. `externals/src/googletest -r60 http://googletest.googlecode.com/svn/trunk`).
Here is an example of using the svn:externals properties on a trunk (read via `svn propget`) of a project. This value checks out a copy of Google Test into the `trunk/externals/src/googletest/` directory.
```
[Computer:svn] user$ svn propget svn:externals trunk
externals/src/googletest http://googletest.googlecode.com/svn/trunk
```
# Add the Framework to Your Project #
The next step is to build and add the gtest.framework to your own project. This guide describes two common ways below.
* **Option 1** --- The simplest way to add Google Test to your own project, is to open gtest.xcodeproj (found in the xcode/ directory of the Google Test trunk) and build the framework manually. Then, add the built framework into your project using the "Add->Existing Framework..." from the context menu or "Project->Add..." from the main menu. The gtest.framework is relocatable and contains the headers and object code that you'll need to make tests. This method requires rebuilding every time you upgrade Google Test in your project.
* **Option 2** --- If you are going to be living off the trunk of Google Test, incorporating its latest features into your unit tests (or are a Google Test developer yourself). You'll want to rebuild the framework every time the source updates. to do this, you'll need to add the gtest.xcodeproj file, not the framework itself, to your own Xcode project. Then, from the build products that are revealed by the project's disclosure triangle, you can find the gtest.framework, which can be added to your targets (discussed below).
# Make a Test Target #
To start writing tests, make a new "Shell Tool" target. This target template is available under BSD, Cocoa, or Carbon. Add your unit test source code to the "Compile Sources" build phase of the target.
Next, you'll want to add gtest.framework in two different ways, depending upon which option you chose above.
* **Option 1** --- During compilation, Xcode will need to know that you are linking against the gtest.framework. Add the gtest.framework to the "Link Binary with Libraries" build phase of your test target. This will include the Google Test headers in your header search path, and will tell the linker where to find the library.
* **Option 2** --- If your working out of the trunk, you'll also want to add gtest.framework to your "Link Binary with Libraries" build phase of your test target. In addition, you'll want to add the gtest.framework as a dependency to your unit test target. This way, Xcode will make sure that gtest.framework is up to date, every time your build your target. Finally, if you don't share build directories with Google Test, you'll have to copy the gtest.framework into your own build products directory using a "Run Script" build phase.
# Set Up the Executable Run Environment #
Since the unit test executable is a shell tool, it doesn't have a bundle with a `Contents/Frameworks` directory, in which to place gtest.framework. Instead, the dynamic linker must be told at runtime to search for the framework in another location. This can be accomplished by setting the "DYLD\_FRAMEWORK\_PATH" environment variable in the "Edit Active Executable ..." Arguments tab, under "Variables to be set in the environment:". The path for this value is the path (relative or absolute) of the directory containing the gtest.framework.
If you haven't set up the DYLD\_FRAMEWORK\_PATH, correctly, you might get a message like this:
```
[Session started at 2008-08-15 06:23:57 -0600.]
dyld: Library not loaded: @loader_path/../Frameworks/gtest.framework/Versions/A/gtest
Referenced from: /Users/username/Documents/Sandbox/gtestSample/build/Debug/WidgetFrameworkTest
Reason: image not found
```
To correct this problem, got to the directory containing the executable named in "Referenced from:" value in the error message above. Then, with the terminal in this location, find the relative path to the directory containing the gtest.framework. That is the value you'll need to set as the DYLD\_FRAMEWORK\_PATH.
# Build and Go #
Now, when you click "Build and Go", the test will be executed. Dumping out something like this:
```
[Session started at 2008-08-06 06:36:13 -0600.]
[==========] Running 2 tests from 1 test case.
[----------] Global test environment set-up.
[----------] 2 tests from WidgetInitializerTest
[ RUN ] WidgetInitializerTest.TestConstructor
[ OK ] WidgetInitializerTest.TestConstructor
[ RUN ] WidgetInitializerTest.TestConversion
[ OK ] WidgetInitializerTest.TestConversion
[----------] Global test environment tear-down
[==========] 2 tests from 1 test case ran.
[ PASSED ] 2 tests.
The Debugger has exited with status 0.
```
# Summary #
Unit testing is a valuable way to ensure your data model stays valid even during rapid development or refactoring. The Google Testing Framework is a great unit testing framework for C and C++ which integrates well with an Xcode development environment.
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