Merge branch 'master' into fix-argc

googletest/docs/advanced.md

+# Advanced googletest Topics
+
+
+## Introduction
+
+Now that you have read the [googletest Primer](primer.md) and learned how to write
+tests using googletest, 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 them.
+
+```c++
+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 googletest's
+output in the future.
+
+```c++
+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, determines the test's success or failure. For example, you
+might want to write something like:
+
+```c++
+switch(expression) {
+  case 1:
+     ... some checks ...
+  case 2:
+     ... some other checks ...
+  default:
+     FAIL() << "We shouldn't get here.";
+}
+```
+
+NOTE: you can only use `FAIL()` in functions that return `void`. See the
+[Assertion Placement section](#assertion-placement) for more information.
+
+**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:
+
+```c++
+ASSERT_THROW(Foo(5), bar_exception);
+
+EXPECT_NO_THROW({
+  int n = 5;
+  Bar(&n);
+});
+```
+
+**Availability**: Linux, Windows, Mac; requires exceptions to be enabled in the
+build environment (note that `google3` **disables** exceptions).
+
+### Predicate Assertions for Better Error Messages
+
+Even though googletest has a rich set of assertions, they can never be complete,
+as it's impossible (nor a good idea) to anticipate all 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.
+
+googletest gives you three different options to solve this problem:
+
+#### Using an Existing Boolean Function
+
+If you already have a function or 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)` is true       |
+| `ASSERT_PRED2(pred2, val1, val2);` | `EXPECT_PRED2(pred2, val1, val2);` | `pred2(val1, val2)` is 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
+
+```c++
+// Returns true if 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
+
+```c++
+  EXPECT_PRED2(MutuallyPrime, a, b);
+```
+
+will succeed, while the assertion
+
+```c++
+  EXPECT_PRED2(MutuallyPrime, b, c);
+```
+
+will fail with the message
+
+```none
+MutuallyPrime(b, c) is false, where
+b is 4
+c is 10
+```
+
+> NOTE:
+>
+> 1.  If you see a compiler error "no matching function to call" when using
+>     `ASSERT_PRED*` or `EXPECT_PRED*`, please see
+>     [this](faq.md#OverloadedPredicate) for how to resolve it.
+> 1.  Currently we only provide predicate assertions of arity <= 5. If you need
+>     a higher-arity assertion, let [us](https://github.com/google/googletest/issues) 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:
+
+```c++
+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:
+
+```c++
+::testing::AssertionResult IsEven(int n) {
+  if ((n % 2) == 0)
+     return ::testing::AssertionSuccess();
+  else
+     return ::testing::AssertionFailure() << n << " is odd";
+}
+```
+
+instead of:
+
+```c++
+bool IsEven(int n) {
+  return (n % 2) == 0;
+}
+```
+
+the failed assertion `EXPECT_TRUE(IsEven(Fib(4)))` will print:
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false (3 is odd)
+Expected: true
+```
+
+instead of a more opaque
+
+```none
+Value of: IsEven(Fib(4))
+  Actual: false
+Expected: true
+```
+
+If you want informative messages in `EXPECT_FALSE` and `ASSERT_FALSE` as well
+(one third of Boolean assertions in the Google code base are negative ones), and
+are fine with making the predicate slower in the success case, you can supply a
+success message:
+
+```c++
+::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
+
+```none
+  Value of: IsEven(Fib(6))
+     Actual: true (8 is even)
+  Expected: false
+```
+
+**Availability**: Linux, Windows, Mac.
+
+#### 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 group 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:
+
+```c++
+::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.
+
+As an example, let's improve the failure message in `MutuallyPrime()`, which was
+used with `EXPECT_PRED2()`:
+
+```c++
+// 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
+
+```c++
+  EXPECT_PRED_FORMAT2(AssertMutuallyPrime, b, c);
+```
+
+to generate the message
+
+```none
+b and c (4 and 10) are not mutually prime, as they have a common divisor 2.
+```
+
+As you may have realized, many of the built-in 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 googletest
+provides assertions to do this. Full details about ULPs are quite long; if you
+want to learn more, see
+[here](https://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/).
+
+#### Floating-Point Macros
+
+| Fatal assertion                 | Nonfatal assertion             | Verifies                                 |
+| ------------------------------- | ------------------------------ | ---------------------------------------- |
+| `ASSERT_FLOAT_EQ(val1, val2);`  | `EXPECT_FLOAT_EQ(val1,val2);`  | the two `float` values are almost equal  |
+| `ASSERT_DOUBLE_EQ(val1, val2);` | `EXPECT_DOUBLE_EQ(val1, val2);`| the two `double` values are almost equal |
+
+By "almost equal" we mean the values are within 4 ULP's from each other.
+
+NOTE: `CHECK_DOUBLE_EQ()` in `base/logging.h` uses a fixed absolute error bound,
+so its result may differ from that of the googletest macros. That macro is
+unsafe and has been deprecated. Please don't use it any more.
+
+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).
+
+```c++
+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.
+
+### Asserting Using gMock Matchers
+
+Google-developed C++ mocking framework [gMock](../../googlemock) comes with a
+library of matchers for validating arguments passed to mock objects. A gMock
+*matcher* is basically a predicate that knows how to describe itself. It can be
+used in these assertion macros:
+
+| Fatal assertion                | Nonfatal assertion             | Verifies              |
+| ------------------------------ | ------------------------------ | --------------------- |
+| `ASSERT_THAT(value, matcher);` | `EXPECT_THAT(value, matcher);` | value matches matcher |
+
+For example, `StartsWith(prefix)` is a matcher that matches a string starting
+with `prefix`, and you can write:
+
+```c++
+using ::testing::StartsWith;
+...
+    // Verifies that Foo() returns a string starting with "Hello".
+    EXPECT_THAT(Foo(), StartsWith("Hello"));
+```
+
+Read this [recipe](../../googlemock/docs/CookBook.md#using-matchers-in-google-test-assertions) in
+the gMock Cookbook for more details.
+
+gMock has a rich set of matchers. You can do many things googletest cannot do
+alone with them. For a list of matchers gMock provides, read
+[this](../../googlemock/docs/CookBook.md#using-matchers). Especially useful among them are
+some [protocol buffer matchers](https://github.com/google/nucleus/blob/master/nucleus/testing/protocol-buffer-matchers.h). It's easy to write
+your [own matchers](../../googlemock/docs/CookBook.md#writing-new-matchers-quickly) too.
+
+For example, you can use gMock's
+[EqualsProto](https://github.com/google/nucleus/blob/master/nucleus/testing/protocol-buffer-matchers.h)
+to compare protos in your tests:
+
+```c++
+#include "testing/base/public/gmock.h"
+using ::testing::EqualsProto;
+...
+    EXPECT_THAT(actual_proto, EqualsProto("foo: 123 bar: 'xyz'"));
+    EXPECT_THAT(*actual_proto_ptr, EqualsProto(expected_proto));
+```
+
+gMock is bundled with googletest, so you don't need to add any build dependency
+in order to take advantage of this. Just include `"testing/base/public/gmock.h"`
+and you're ready to go.
+
+**Availability**: Linux, Windows, and Mac.
+
+### More String Assertions
+
+(Please read the [previous](#AssertThat) section first if you haven't.)
+
+You can use the gMock [string matchers](../../googlemock/docs/CheatSheet.md#string-matchers)
+with `EXPECT_THAT()` or `ASSERT_THAT()` to do more string comparison tricks
+(sub-string, prefix, suffix, regular expression, and etc). For example,
+
+```c++
+using ::testing::HasSubstr;
+using ::testing::MatchesRegex;
+...
+  ASSERT_THAT(foo_string, HasSubstr("needle"));
+  EXPECT_THAT(bar_string, MatchesRegex("\\w*\\d+"));
+```
+
+**Availability**: Linux, Windows, Mac.
+
+If the string contains a well-formed HTML or XML document, you can check whether
+its DOM tree matches an [XPath
+expression](http://www.w3.org/TR/xpath/#contents):
+
+```c++
+// Currently still in //template/prototemplate/testing:xpath_matcher
+#include "template/prototemplate/testing/xpath_matcher.h"
+using prototemplate::testing::MatchesXPath;
+EXPECT_THAT(html_string, MatchesXPath("//a[text()='click here']"));
+```
+
+**Availability**: Linux.
+
+### 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:
+
+```c++
+CComPtr<IShellDispatch2> 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
+
+```c++
+::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:
+
+```c++
+template <typename T> class Foo {
+ public:
+  void Bar() { ::testing::StaticAssertTypeEq<int, T>(); }
+};
+```
+
+the code:
+
+```c++
+void Test1() { Foo<bool> foo; }
+```
+
+will not generate a compiler error, as `Foo<bool>::Bar()` is never actually
+instantiated. Instead, you need:
+
+```c++
+void Test2() { Foo<bool> foo; foo.Bar(); }
+```
+
+to cause a compiler error.
+
+**Availability**: Linux, Windows, Mac.
+
+### 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's 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"` or `"cannot
+initialize return object of type 'bool' with an rvalue of type 'void'"` or
+`"error: no viable conversion from 'void' to 'string'"`.
+
+If you need to use fatal 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 googletest How to Print Your Values
+
+When a test assertion such as `EXPECT_EQ` fails, googletest 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:
+
+```c++
+// Streams are allowed only for logging.  Don't include this for
+// any other purpose.
+#include <ostream>
+
+namespace foo {
+
+class Bar {  // We want googletest to be able to print instances of this.
+...
+  // Create a free inline friend function.
+  friend ::std::ostream& operator<<(::std::ostream& os, const Bar& bar) {
+    return os << bar.DebugString();  // whatever needed to print bar to os
+  }
+};
+
+// If you can't declare the function in the class 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:
+
+```c++
+// Streams are allowed only for logging.  Don't include this for
+// any other purpose.
+#include <ostream>
+
+namespace foo {
+
+class Bar {
+  ...
+  friend void PrintTo(const Bar& bar, ::std::ostream* os) {
+    *os << bar.DebugString();  // whatever needed to print bar to os
+  }
+};
+
+// If you can't declare the function in the class 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
+googletest is concerned. This allows you to customize how the value appears in
+googletest's output without affecting code that relies on the behavior of its
+`<<` operator.
+
+If you want to print a value `x` using googletest's value printer yourself, just
+call `::testing::PrintToString(x)`, which returns an `std::string`:
+
+```c++
+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](#ExceptionAssertions).
+
+If you want to test `EXPECT_*()/ASSERT_*()` failures in your test code, see
+Catching Failures
+
+### How to Write a Death Test
+
+googletest 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 (Perl) 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`. googletest defines a few
+predicates that handle the most common cases:
+
+```c++
+::testing::ExitedWithCode(exit_code)
+```
+
+This expression is `true` if the program exited normally with the given exit
+code.
+
+```c++
+::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?
+2.  (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
+3.  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 googletest assertions don't abort
+the process.
+
+To write a death test, simply use one of the above macros inside your test
+function. For example,
+
+```c++
+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.
+
+### Death Test Naming
+
+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](#death-tests-and-threads) section below explains why.
+
+If a test fixture class is shared by normal tests and death tests, you can use
+`using` or `typedef` to introduce an alias for the fixture class and avoid
+duplicating its code:
+
+```c++
+class FooTest : public ::testing::Test { ... };
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooTest, DoesThis) {
+  // normal test
+}
+
+TEST_F(FooDeathTest, DoesThat) {
+  // death test
+}
+```
+
+**Availability**: Linux, Windows (requires MSVC 8.0 or above), Cygwin, and Mac
+
+### Regular Expression Syntax
+
+
+On POSIX systems (e.g. Linux, Cygwin, and Mac), googletest uses the
+[POSIX extended regular expression](http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html#tag_09_04)
+syntax. 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, googletest uses its own simple regular expression implementation. It
+lacks many features. 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.):
+
+Expression | Meaning
+---------- | --------------------------------------------------------------
+`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, googletest
+defines macros to govern which regular expression it is using. The macros are:
+<!--absl:google3-begin(google3-only)-->`GTEST_USES_PCRE=1`, or
+<!--absl:google3-end--> `GTEST_USES_SIMPLE_RE=1` or `GTEST_USES_POSIX_RE=1`. If
+you want your death tests to work in all 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
+2.  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.
+
+googletest 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.
+2.  Test cases with a name ending in "DeathTest" are run before all other tests.
+3.  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.
+
+The automated testing framework does not set the style flag. You can choose a
+particular style of death tests by setting the flag programmatically:
+
+```c++
+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:
+
+```c++
+int main(int argc, char** argv) {
+  InitGoogle(argv[0], &argc, &argv, true);
+  ::testing::FLAGS_gtest_death_test_style = "fast";
+  return RUN_ALL_TESTS();
+}
+
+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(), "");
+}
+```
+
+
+### 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 googletest 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;
+2.  free the memory again in the parent process; or
+3.  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 or the `ScopedTrace` utility:
+
+```c++
+SCOPED_TRACE(message);
+ScopedTrace trace("file_path", line_number, message);
+```
+
+where `message` can be anything streamable to `std::ostream`. `SCOPED_TRACE`
+macro will cause the current file name, line number, and the given message to be
+added in every failure message. `ScopedTrace` accepts explicit file name and
+line number in arguments, which is useful for writing test helpers. The effect
+will be undone when the control leaves the current lexical scope.
+
+For example,
+
+```c++
+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:
+
+```none
+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.
+2.  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.
+3.  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 `""`.
+4.  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.
+5.  The trace dump is clickable in Emacs - 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:
+
+```c++
+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!
+}
+```
+
+To alleviate this, googletest provides three different solutions. You could use
+either exceptions, the `(ASSERT|EXPECT)_NO_FATAL_FAILURE` assertions or the
+`HasFatalFailure()` function. They are described in the following two
+subsections.
+
+#### Asserting on Subroutines with an exception
+
+The following code can turn ASSERT-failure into an exception:
+
+```c++
+class ThrowListener : public testing::EmptyTestEventListener {
+  void OnTestPartResult(const testing::TestPartResult& result) override {
+    if (result.type() == testing::TestPartResult::kFatalFailure) {
+      throw testing::AssertionException(result);
+    }
+  }
+};
+int main(int argc, char** argv) {
+  ...
+  testing::UnitTest::GetInstance()->listeners().Append(new ThrowListener);
+  return RUN_ALL_TESTS();
+}
+```
+
+This listener should be added after other listeners if you have any, otherwise
+they won't see failed `OnTestPartResult`.
+
+#### 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
+googletest 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:
+
+```c++
+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 on Windows.
+
+#### 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.
+
+```c++
+class Test {
+ public:
+  ...
+  static bool HasFatalFailure();
+};
+```
+
+The typical usage, which basically simulates the behavior of a thrown exception,
+is:
+
+```c++
+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:
+
+```c++
+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.
+
+## 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](#XmlReport) if you
+specify one. For example, the test
+
+```c++
+TEST_F(WidgetUsageTest, MinAndMaxWidgets) {
+  RecordProperty("MaximumWidgets", ComputeMaxUsage());
+  RecordProperty("MinimumWidgets", ComputeMinUsage());
+}
+```
+
+will output XML like this:
+
+```xml
+  ...
+    <testcase name="MinAndMaxWidgets" status="run" time="0.006" 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 googletest (`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
+
+googletest 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 their sharing a
+single resource copy. So, in addition to per-test set-up/tear-down, googletest
+also supports per-test-case set-up/tear-down. To use it:
+
+1.  In your test fixture class (say `FooTest` ), declare as `static` some member
+    variables to hold the shared resources.
+1.  Outside your test fixture class (typically just below it), define those
+    member variables, optionally giving them initial values.
+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! googletest 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:
+
+```c++
+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 logic as usual.
+  virtual void SetUp() { ... }
+
+  // You can define per-test tear-down logic as usual.
+  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 ...
+}
+```
+
+NOTE: Though the above code declares `SetUpTestCase()` protected, it may
+sometimes be necessary to declare it public, such as when using it with
+`TEST_P`.
+
+**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:
+
+```c++
+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 googletest by
+calling the `::testing::AddGlobalTestEnvironment()` function:
+
+```c++
+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 googletest 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:
+
+```c++
+::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).
+
+## Value-Parameterized Tests
+
+*Value-parameterized tests* allow you to test your code with different
+parameters without writing multiple copies of the same test. This is useful in a
+number of situations, for example:
+
+*   You have a piece of code whose behavior is affected by one or more
+    command-line flags. You want to make sure your code performs correctly for
+    various values of those flags.
+*   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.
+
+NOTE: If your test fixture defines `SetUpTestCase()` or `TearDownTestCase()`
+they must be declared **public** rather than **protected** in order to use
+`TEST_P`.
+
+```c++
+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.
+
+```c++
+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. googletest 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:
+
+| Parameter Generator          | Behavior                                    |
+| ---------------------------- | ------------------------------------------- |
+| `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)`. |
+| `Bool()`                     | Yields sequence `{false, true}`.            |
+| `Combine(g1, g2, ..., gN)`   | Yields all combinations (Cartesian product) as std\:\:tuples of the values generated by the `N` generators.            |
+
+For more details, see the comments at the definitions of these functions.
+
+The following statement will instantiate tests from the `FooTest` test case each
+with parameter values `"meeny"`, `"miny"`, and `"moe"`.
+
+```c++
+INSTANTIATE_TEST_CASE_P(InstantiationName,
+                        FooTest,
+                        ::testing::Values("meeny", "miny", "moe"));
+```
+
+NOTE: The code above must be placed at global or namespace scope, not at
+function scope.
+
+NOTE: Don't forget this step! If you do your test will silently pass, but none
+of its cases will ever run!
+
+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`](#TestFilter).
+
+This statement will instantiate all tests from `FooTest` again, each with
+parameter values `"cat"` and `"dog"`:
+
+```c++
+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 sample7_unittest.cc and sample8_unittest.cc for more examples.
+
+**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac
+
+### 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 *abstract tests*.
+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, they 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 depending on the library target that
+contains `foo_param_test.cc`. You can instantiate the same abstract test case
+multiple times, possibly in different source files.
+
+### Specifying Names for Value-Parameterized Test Parameters
+
+The optional last argument to `INSTANTIATE_TEST_CASE_P()` allows the user to
+specify a function or functor that generates custom test name suffixes based on
+the test parameters. The function should accept one argument of type
+`testing::TestParamInfo<class ParamType>`, and return `std::string`.
+
+`testing::PrintToStringParamName` is a builtin test suffix generator that
+returns the value of `testing::PrintToString(GetParam())`. It does not work for
+`std::string` or C strings.
+
+NOTE: test names must be non-empty, unique, and may only contain ASCII
+alphanumeric characters. In particular, they [should not contain
+underscores](https://g3doc.corp.google.com/third_party/googletest/googletest/g3doc/faq.md#no-underscores).
+
+```c++
+class MyTestCase : public testing::TestWithParam<int> {};
+
+TEST_P(MyTestCase, MyTest)
+{
+  std::cout << "Example Test Param: " << GetParam() << std::endl;
+}
+
+INSTANTIATE_TEST_CASE_P(MyGroup, MyTestCase, testing::Range(0, 10),
+                        testing::PrintToStringParamName());
+```
+
+## Typed Tests</id>
+
+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`:
+
+```c++
+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:
+
+```c++
+using MyTypes = ::testing::Types<char, int, unsigned int>;
+TYPED_TEST_CASE(FooTest, MyTypes);
+```
+
+The type alias (`using` or `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:
+
+```c++
+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 sample6_unittest.cc
+
+**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac
+
+## 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 their 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:
+
+```c++
+template <typename T>
+class FooTest : public ::testing::Test {
+  ...
+};
+```
+
+Next, declare that you will define a type-parameterized test case:
+
+```c++
+TYPED_TEST_CASE_P(FooTest);
+```
+
+Then, use `TYPED_TEST_P()` to define a type-parameterized test. You can repeat
+this as many times as you want:
+
+```c++
+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:
+
+```c++
+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.
+
+```c++
+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:
+
+```c++
+INSTANTIATE_TYPED_TEST_CASE_P(My, FooTest, int);
+```
+
+You can see `sample6_unittest.cc` for a complete example.
+
+**Availability**: Linux, Windows (requires MSVC 8.0 or above), Mac
+
+## 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.** The desire to test internal
+implementation is often a sign that the class is doing too much. Consider
+extracting an implementation class, and testing it. Then use that implementation
+class in the original class.
+
+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
+
+To test them, we use the following special techniques:
+
+*   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.
+    (#including `.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 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](https://www.gamedev.net/articles/programming/general-and-gameplay-programming/the-c-pimpl-r1794/)
+    (Private Implementation) idiom.
+
+    Or, you can declare an individual test as a friend of your class by adding
+    this line in the class body:
+
+    ```c++
+        FRIEND_TEST(TestCaseName, TestName);
+    ```
+
+    For example,
+
+    ```c++
+    // foo.h
+
+    #include "gtest/gtest_prod.h"
+
+    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:
+
+    ```c++
+    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:
+
+    ```c++
+    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 googletest, you'll want to test
+your utility. What framework would you use to test it? googletest, 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 googletest doesn't use exceptions, so how do
+we test that a piece of code generates an expected failure?
+
+gunit-spi.h contains some constructs to do this. After #including this header,
+you can use
+
+```c++
+  EXPECT_FATAL_FAILURE(statement, substring);
+```
+
+to assert that `statement` generates a fatal (e.g. `ASSERT_*`) failure in the
+current thread whose message contains the given `substring`, or use
+
+```c++
+  EXPECT_NONFATAL_FAILURE(statement, substring);
+```
+
+if you are expecting a non-fatal (e.g. `EXPECT_*`) failure.
+
+Only failures in the current thread are checked to determine the result of this
+type of expectations. If `statement` creates new threads, failures in these
+threads are also ignored. If you want to catch failures in other threads as
+well, use one of the following macros instead:
+
+```c++
+  EXPECT_FATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+  EXPECT_NONFATAL_FAILURE_ON_ALL_THREADS(statement, substring);
+```
+
+NOTE: Assertions from multiple threads are currently not supported on Windows.
+
+For technical reasons, there are some caveats:
+
+1.  You cannot stream a failure message to either macro.
+
+1.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()` cannot reference
+    local non-static variables or non-static members of `this` object.
+
+1.  `statement` in `EXPECT_FATAL_FAILURE{_ON_ALL_THREADS}()()` cannot return a
+    value.
+
+
+## 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:
+
+```c++
+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;
+};
+
+}
+```
+
+To obtain a `TestInfo` object for the currently running test, call
+`current_test_info()` on the `UnitTest` singleton object:
+
+```c++
+  // 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 googletest by Handling Test Events
+
+googletest provides an **event listener API** 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.
+
+### Defining Event Listeners
+
+To define a event listener, you subclass either testing::TestEventListener or
+testing::EmptyTestEventListener The former is an (abstract) interface, where
+*each pure virtual method can be overridden to handle a test event* (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 reflects the state of the entire test program,
+*   TestCase has information about a test case, which can contain one or more
+    tests,
+*   TestInfo contains the state of a test, and
+*   TestPartResult 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:
+
+```c++
+  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 SUCCESS().
+    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
+googletest event listener list (represented by class TestEventListeners - note
+the "s" at the end of the name) in your `main()` function, before calling
+`RUN_ALL_TESTS()`:
+
+```c++
+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.  googletest 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:
+
+```c++
+  ...
+  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 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 sample10_unittest.cc
+
+## Running Test Programs: Advanced Options
+
+googletest 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.
+
+If an option is specified both by an environment variable and by a flag, the
+latter takes precedence.
+
+### Selecting Tests
+
+#### 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:
+
+```none
+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 googletest 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, googletest 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`.
+*   `./foo_test --gtest_filter=FooTest.*:BarTest.*-FooTest.Bar:BarTest.Foo` Runs
+    everything in test case `FooTest` except `FooTest.Bar` and everything in
+    test case `BarTest` except `BarTest.Foo`.
+    
+#### 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 googletest, even though they
+will still be compiled:
+
+```c++
+// 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, googletest 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 `gsearch`
+and/or `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 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` flag to further select which
+disabled tests to run.
+
+**Availability**: Linux, Windows, Mac.
+
+### 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:
+
+```none
+$ 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 test
+fails, 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](#GlobalSetUp) code, 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, googletest 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 in the range [0, 99999]. The seed value 0 is special: it tells
+googletest to do the default behavior of calculating the seed from the current
+time.
+
+If you combine this with `--gtest_repeat=N`, googletest will pick a different
+random seed and re-shuffle the tests in each iteration.
+
+**Availability**: Linux, Windows, Mac.
+
+### Controlling Test Output
+
+#### Colored Terminal Output
+
+googletest can use colors in its terminal output to make it easier to spot the
+important information:
+
+...<br/>
+<span style="color:green">[----------]<span style="color:black"> 1 test from FooTest<br/>
+<span style="color:green">[ RUN      ]<span style="color:black"> FooTest.DoesAbc<br/>
+<span style="color:green">[       OK ]<span style="color:black"> FooTest.DoesAbc<br/>
+<span style="color:green">[----------]<span style="color:black"> 2 tests from BarTest<br/>
+<span style="color:green">[ RUN      ]<span style="color:black"> BarTest.HasXyzProperty<br/>
+<span style="color:green">[       OK ]<span style="color:black"> BarTest.HasXyzProperty<br/>
+<span style="color:green">[ RUN      ]<span style="color:black"> BarTest.ReturnsTrueOnSuccess<br/>
+... some error messages ...<br/>
+<span   style="color:red">[  FAILED  ] <span style="color:black">BarTest.ReturnsTrueOnSuccess<br/>
+...<br/>
+<span style="color:green">[==========]<span style="color:black"> 30 tests from 14 test cases ran.<br/>
+<span style="color:green">[  PASSED  ]<span style="color:black"> 28 tests.<br/>
+<span style="color:red">[  FAILED  ]<span style="color:black"> 2 tests, listed below:<br/>
+<span style="color:red">[  FAILED  ]<span style="color:black"> BarTest.ReturnsTrueOnSuccess<br/>
+<span style="color:red">[  FAILED  ]<span style="color:black"> AnotherTest.DoesXyz<br/>
+  2 FAILED TESTS
+
+You can set the `GTEST_COLOR` environment variable or the `--gtest_color`
+command line flag to `yes`, `no`, or `auto` (the default) to enable colors,
+disable colors, or let googletest decide. When the value is `auto`, googletest
+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, googletest prints the time it takes to run each test. To disable
+that, run the test program with the `--gtest_print_time=0` command line flag, or
+set the GTEST_PRINT_TIME environment variable to `0`.
+
+**Availability**: Linux, Windows, Mac.
+
+#### Suppressing UTF-8 Text Output
+
+In case of assertion failures, googletest prints expected and actual values of
+type `string` both as hex-encoded strings as well as in readable UTF-8 text if
+they contain valid non-ASCII UTF-8 characters. If you want to suppress the UTF-8
+text because, for example, you don't have an UTF-8 compatible output medium, run
+the test program with `--gtest_print_utf8=0` or set the `GTEST_PRINT_UTF8`
+environment variable to `0`.
+
+**Availability**: Linux, Windows, Mac.
+
+
+#### Generating an XML Report
+
+googletest 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. The report is also used by the http://unittest
+dashboard to show per-test-method error messages.
+
+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), googletest 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), googletest will pick a different name (e.g.
+`foo_test_1.xml`) to avoid overwriting it.
+
+
+The report is based on the `junitreport` Ant task. Since that format was
+originally intended for Java, a little interpretation is required to make it
+apply to googletest tests, as shown here:
+
+```xml
+<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 googletest test cases.
+*   `<testcase>` elements correspond to googletest test functions.
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<testsuites tests="3" failures="1" errors="0" time="0.035" timestamp="2011-10-31T18:52:42" name="AllTests">
+  <testsuite name="MathTest" tests="2" failures="1" errors="0" time="0.015">
+    <testcase name="Addition" status="run" time="0.007" classname="">
+      <failure message="Value of: add(1, 1)&#x0A;  Actual: 3&#x0A;Expected: 2" type="">...</failure>
+      <failure message="Value of: add(1, -1)&#x0A;  Actual: 1&#x0A;Expected: 0" type="">...</failure>
+    </testcase>
+    <testcase name="Subtraction" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+  <testsuite name="LogicTest" tests="1" failures="0" errors="0" time="0.005">
+    <testcase name="NonContradiction" status="run" time="0.005" classname="">
+    </testcase>
+  </testsuite>
+</testsuites>
+```
+
+Things to note:
+
+*   The `tests` attribute of a `<testsuites>` or `<testsuite>` element tells how
+    many test functions the googletest 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 seconds.
+
+*   The `timestamp` attribute records the local date and time of the test
+    execution.
+
+*   Each `<failure>` element corresponds to a single failed googletest
+    assertion.
+
+**Availability**: Linux, Windows, Mac.
+
+#### Generating an JSON Report
+
+googletest can also emit a JSON report as an alternative format to XML. To
+generate the JSON report, set the `GTEST_OUTPUT` environment variable or the
+`--gtest_output` flag to the string `"json:path_to_output_file"`, which will
+create the file at the given location. You can also just use the string
+`"json"`, in which case the output can be found in the `test_detail.json` file
+in the current directory.
+
+The report format conforms to the following JSON Schema:
+
+```json
+{
+  "$schema": "http://json-schema.org/schema#",
+  "type": "object",
+  "definitions": {
+    "TestCase": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "tests": { "type": "integer" },
+        "failures": { "type": "integer" },
+        "disabled": { "type": "integer" },
+        "time": { "type": "string" },
+        "testsuite": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/TestInfo"
+          }
+        }
+      }
+    },
+    "TestInfo": {
+      "type": "object",
+      "properties": {
+        "name": { "type": "string" },
+        "status": {
+          "type": "string",
+          "enum": ["RUN", "NOTRUN"]
+        },
+        "time": { "type": "string" },
+        "classname": { "type": "string" },
+        "failures": {
+          "type": "array",
+          "items": {
+            "$ref": "#/definitions/Failure"
+          }
+        }
+      }
+    },
+    "Failure": {
+      "type": "object",
+      "properties": {
+        "failures": { "type": "string" },
+        "type": { "type": "string" }
+      }
+    }
+  },
+  "properties": {
+    "tests": { "type": "integer" },
+    "failures": { "type": "integer" },
+    "disabled": { "type": "integer" },
+    "errors": { "type": "integer" },
+    "timestamp": {
+      "type": "string",
+      "format": "date-time"
+    },
+    "time": { "type": "string" },
+    "name": { "type": "string" },
+    "testsuites": {
+      "type": "array",
+      "items": {
+        "$ref": "#/definitions/TestCase"
+      }
+    }
+  }
+}
+```
+
+The report uses the format that conforms to the following Proto3 using the [JSON
+encoding](https://developers.google.com/protocol-buffers/docs/proto3#json):
+
+```proto
+syntax = "proto3";
+
+package googletest;
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/duration.proto";
+
+message UnitTest {
+  int32 tests = 1;
+  int32 failures = 2;
+  int32 disabled = 3;
+  int32 errors = 4;
+  google.protobuf.Timestamp timestamp = 5;
+  google.protobuf.Duration time = 6;
+  string name = 7;
+  repeated TestCase testsuites = 8;
+}
+
+message TestCase {
+  string name = 1;
+  int32 tests = 2;
+  int32 failures = 3;
+  int32 disabled = 4;
+  int32 errors = 5;
+  google.protobuf.Duration time = 6;
+  repeated TestInfo testsuite = 7;
+}
+
+message TestInfo {
+  string name = 1;
+  enum Status {
+    RUN = 0;
+    NOTRUN = 1;
+  }
+  Status status = 2;
+  google.protobuf.Duration time = 3;
+  string classname = 4;
+  message Failure {
+    string failures = 1;
+    string type = 2;
+  }
+  repeated Failure failures = 5;
+}
+```
+
+For instance, the following program
+
+```c++
+TEST(MathTest, Addition) { ... }
+TEST(MathTest, Subtraction) { ... }
+TEST(LogicTest, NonContradiction) { ... }
+```
+
+could generate this report:
+
+```json
+{
+  "tests": 3,
+  "failures": 1,
+  "errors": 0,
+  "time": "0.035s",
+  "timestamp": "2011-10-31T18:52:42Z"
+  "name": "AllTests",
+  "testsuites": [
+    {
+      "name": "MathTest",
+      "tests": 2,
+      "failures": 1,
+      "errors": 0,
+      "time": "0.015s",
+      "testsuite": [
+        {
+          "name": "Addition",
+          "status": "RUN",
+          "time": "0.007s",
+          "classname": "",
+          "failures": [
+            {
+              "message": "Value of: add(1, 1)\x0A  Actual: 3\x0AExpected: 2",
+              "type": ""
+            },
+            {
+              "message": "Value of: add(1, -1)\x0A  Actual: 1\x0AExpected: 0",
+              "type": ""
+            }
+          ]
+        },
+        {
+          "name": "Subtraction",
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    }
+    {
+      "name": "LogicTest",
+      "tests": 1,
+      "failures": 0,
+      "errors": 0,
+      "time": "0.005s",
+      "testsuite": [
+        {
+          "name": "NonContradiction",
+          "status": "RUN",
+          "time": "0.005s",
+          "classname": ""
+        }
+      ]
+    }
+  ]
+}
+```
+
+IMPORTANT: The exact format of the JSON document is subject to change.
+
+**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. googletest'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
+
+googletest 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
+googletest 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.
+

googletest/docs/faq.md

+# Googletest FAQ
+
+
+## Why should test case names and test names not 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 contains 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:
+
+```c++
+TEST(Time, Flies_Like_An_Arrow) { ... }
+TEST(Time_Flies, Like_An_Arrow) { ... }
+```
+
+Now, the two `TEST`s will both generate the same class
+(`Time_Flies_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 googletest some wiggle room in case its
+implementation needs to change in the future.
+
+If you violate the rule, there may not be immediate 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 googletest. Therefore it's best to follow
+the rule.
+
+## Why does googletest support `EXPECT_EQ(NULL, ptr)` and `ASSERT_EQ(NULL, ptr)` but not `EXPECT_NE(NULL, ptr)` and `ASSERT_NE(NULL, ptr)`?
+
+First of all you can use `EXPECT_NE(nullptr, ptr)` and `ASSERT_NE(nullptr,
+ptr)`. This is the preferred syntax in the style guide because nullptr does not
+have the type problems that NULL does. Which is why NULL does not work.
+
+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 googletest 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 the gMock matcher 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.
+
+## I need to test that different implementations of an interface satisfy some common requirements. Should I use typed tests or value-parameterized tests?
+
+For testing various implementations of the same interface, either typed tests or
+value-parameterized tests can get it done. It's really up to you the user to
+decide which is more convenient for you, depending on your particular case. Some
+rough guidelines:
+
+*   Typed tests can be easier to write if instances of the different
+    implementations can be created the same way, modulo the type. For example,
+    if all these implementations have a public default constructor (such that
+    you can write `new TypeParam`), or if their factory functions have the same
+    form (e.g. `CreateInstance<TypeParam>()`).
+*   Value-parameterized tests can be easier to write if you need different code
+    patterns to create different implementations' instances, e.g. `new Foo` vs
+    `new Bar(5)`. To accommodate for the differences, you can write factory
+    function wrappers and pass these function pointers to the tests as their
+    parameters.
+*   When a typed test fails, the output includes the name of the type, which can
+    help you quickly identify which implementation is wrong. Value-parameterized
+    tests cannot do this, so there you'll have to look at the iteration number
+    to know which implementation the failure is from, which is less direct.
+*   If you make a mistake writing a typed test, the compiler errors can be
+    harder to digest, as the code is templatized.
+*   When using typed tests, you need to make sure you are testing against the
+    interface type, not the concrete types (in other words, you want to make
+    sure `implicit_cast<MyInterface*>(my_concrete_impl)` works, not just that
+    `my_concrete_impl` works). It's less likely to make mistakes in this area
+    when using value-parameterized tests.
+
+I hope I didn't confuse you more. :-) If you don't mind, I'd suggest you to give
+both approaches a try. Practice is a much better way to grasp the subtle
+differences between the two tools. Once you have some concrete experience, you
+can much more easily decide which one to use the next time.
+
+## My death tests became very slow - what happened?
+
+In August 2008 we had to switch the default death test style from `fast` to
+`threadsafe`, as the former is no longer safe now that threaded logging is the
+default. This caused many death tests to slow down. Unfortunately this change
+was necessary.
+
+Please read [Fixing Failing Death Tests](death_test_styles.md) for what you can
+do.
+
+## I got some run-time errors about invalid proto descriptors when using `ProtocolMessageEquals`. Help!
+
+**Note:** `ProtocolMessageEquals` and `ProtocolMessageEquiv` are *deprecated*
+now. Please use `EqualsProto`, etc instead.
+
+`ProtocolMessageEquals` and `ProtocolMessageEquiv` were redefined recently and
+are now less tolerant on invalid protocol buffer definitions. In particular, if
+you have a `foo.proto` that doesn't fully qualify the type of a protocol message
+it references (e.g. `message<Bar>` where it should be `message<blah.Bar>`), you
+will now get run-time errors like:
+
+```
+... descriptor.cc:...] Invalid proto descriptor for file "path/to/foo.proto":
+... descriptor.cc:...]  blah.MyMessage.my_field: ".Bar" is not defined.
+```
+
+If you see this, your `.proto` file is broken and needs to be fixed by making
+the types fully qualified. The new definition of `ProtocolMessageEquals` and
+`ProtocolMessageEquiv` just happen to reveal your bug.
+
+## 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.
+
+In particular, if you use [gMock](../../googlemock) and the death test statement
+invokes some mock methods, the parent process will think the calls have never
+occurred. Therefore, you may want to move your `EXPECT_CALL` statements inside
+the `EXPECT_DEATH` macro.
+
+## EXPECT_EQ(htonl(blah), blah_blah) generates weird compiler errors in opt mode. Is this a googletest bug?
+
+Actually, the bug is in `htonl()`.
+
+According to `'man htonl'`, `htonl()` is a *function*, which means it's valid to
+use `htonl` as a function pointer. However, in opt mode `htonl()` is defined as
+a *macro*, which breaks this usage.
+
+Worse, the macro definition of `htonl()` uses a `gcc` extension and is *not*
+standard C++. That hacky implementation has some ad hoc limitations. In
+particular, it prevents you from writing `Foo<sizeof(htonl(x))>()`, where `Foo`
+is a template that has an integral argument.
+
+The implementation of `EXPECT_EQ(a, b)` uses `sizeof(... a ...)` inside a
+template argument, and thus doesn't compile in opt mode when `a` contains a call
+to `htonl()`. It is difficult to make `EXPECT_EQ` bypass the `htonl()` bug, as
+the solution must work with different compilers on various platforms.
+
+`htonl()` has some other problems as described in `//util/endian/endian.h`,
+which defines `ghtonl()` to replace it. `ghtonl()` does the same thing `htonl()`
+does, only without its problems. We suggest you to use `ghtonl()` instead of
+`htonl()`, both in your tests and production code.
+
+`//util/endian/endian.h` also defines `ghtons()`, which solves similar problems
+in `htons()`.
+
+Don't forget to add `//util/endian` to the list of dependencies in the `BUILD`
+file wherever `ghtonl()` and `ghtons()` are used. The library consists of a
+single header file and will not bloat your binary.
+
+## 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:
+
+```c++
+// foo.h
+class Foo {
+  ...
+  static const int kBar = 100;
+};
+```
+
+You also need to define it *outside* of the class body in `foo.cc`:
+
+```c++
+const int Foo::kBar;  // No initializer here.
+```
+
+Otherwise your code is **invalid C++**, and may break in unexpected ways. In
+particular, using it in googletest comparison assertions (`EXPECT_EQ`, etc) will
+generate an "undefined reference" linker error. The fact that "it used to work"
+doesn't mean it's valid. It just means that you were lucky. :-)
+
+## 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 googletest, 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:
+
+```c++
+// Defines a base test fixture.
+class BaseTest : public ::testing::Test {
+ protected:
+  ...
+};
+
+// Derives a fixture FooTest from BaseTest.
+class FooTest : public BaseTest {
+ protected:
+  void SetUp() override {
+    BaseTest::SetUp();  // Sets up the base fixture first.
+    ... additional set-up work ...
+  }
+
+  void TearDown() override {
+    ... 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.
+googletest has no limit on how deep the hierarchy can be.
+
+For a complete example using derived test fixtures, see [googletest
+sample](https://github.com/google/googletest/blob/master/googletest/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, due to exceptions being
+disabled by our build system. Please see more details
+[here](advanced.md#assertion-placement).
+
+## My death test hangs (or seg-faults). How do I fix it?
+
+In googletest, 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](advanced.md#how-it-works).
+
+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()`. For example, you may want to use [mocks](../../googlemock)
+or fake objects instead of real ones in your tests.
+
+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 SetUp()/TearDown()?
+
+The first thing to remember is that googletest does **not** reuse the same test
+fixture object across multiple tests. For each `TEST_F`, googletest will create
+a **fresh** test fixture object, immediately call `SetUp()`, run the test body,
+call `TearDown()`, and then delete the test fixture object.
+
+When you need to write per-test set-up and tear-down logic, you have the choice
+between using the test fixture constructor/destructor or `SetUp()/TearDown()`.
+The former is usually preferred, as it has the following benefits:
+
+*   By initializing a member variable in the constructor, we have the option to
+    make it `const`, which helps prevent accidental changes to its value and
+    makes the tests more obviously correct.
+*   In case we need to subclass the test fixture class, the subclass'
+    constructor is guaranteed to call the base class' constructor *first*, and
+    the subclass' destructor is guaranteed to call the base class' destructor
+    *afterward*. With `SetUp()/TearDown()`, a subclass may make the mistake of
+    forgetting to call the base class' `SetUp()/TearDown()` or call them at the
+    wrong time.
+
+You may still want to use `SetUp()/TearDown()` in the following rare cases:
+
+*   In the body of a constructor (or destructor), it's not possible to use the
+    `ASSERT_xx` macros. Therefore, if the set-up operation could cause a fatal
+    test failure that should prevent the test from running, it's necessary to
+    use a `CHECK` macro or to use `SetUp()` instead of a constructor.
+*   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 googletest 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
+    googletest 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
+    overridden in a derived class, you have to use `SetUp()/TearDown()`.
+
+
+## The compiler complains "no matching function to call" when I use ASSERT_PRED*. 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
+
+```c++
+bool IsPositive(int n) {
+  return n > 0;
+}
+
+bool IsPositive(double x) {
+  return x > 0;
+}
+```
+
+you will get a compiler error if you write
+
+```c++
+EXPECT_PRED1(IsPositive, 5);
+```
+
+However, this will work:
+
+```c++
+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
+
+```c++
+template <typename T>
+bool IsNegative(T x) {
+  return x < 0;
+}
+```
+
+you can use it in a predicate assertion like this:
+
+```c++
+ASSERT_PRED1(IsNegative<int>, -5);
+```
+
+Things are more interesting if your template has more than one parameters. The
+following won't compile:
+
+```c++
+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:
+
+```c++
+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
+
+```c++
+  return RUN_ALL_TESTS();
+```
+
+they write
+
+```c++
+  RUN_ALL_TESTS();
+```
+
+This is **wrong and dangerous**. The testing services 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 googletest assertion failure. Very bad.
+
+We have decided to fix this (thanks to Michael Chastain for the idea). Now, your
+code will no longer be able to ignore `RUN_ALL_TESTS()` when compiled with
+`gcc`. If you do so, you'll get a compiler error.
+
+If you see the compiler complaining about you ignoring the return value of
+`RUN_ALL_TESTS()`, the fix is simple: just make sure its value is used as the
+return value of `main()`.
+
+But how could we introduce a change that breaks existing tests? Well, in this
+case, the code was already broken in the first place, so we didn't break it. :-)
+
+## 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.
+
+```c++
+  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](advanced.md#assertion-placement) in the user's guide explains it.
+
+## My SetUp() function is not called. Why?
+
+C++ is case-sensitive. 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?
+
+googletest's failure message format is understood by Emacs and many other IDEs,
+like acme and XCode. If a googletest message is in a compilation buffer in
+Emacs, then it's clickable.
+
+
+## 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
+
+```c++
+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:
+
+```c++
+typedef BaseTest FooTest;
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+typedef BaseTest BarTest;
+
+TEST_F(BarTest, Abc) { ... }
+TEST_F(BarTest, Def) { ... }
+```
+
+## googletest output is buried in a whole bunch of LOG messages. What do I do?
+
+The googletest output is meant to be a concise and human-friendly report. If
+your test generates textual output itself, it will mix with the googletest
+output, making it hard to read. However, there is an easy solution to this
+problem.
+
+Since `LOG` messages go to stderr, we decided to let googletest output go to
+stdout. This way, you can easily separate the two using redirection. For
+example:
+
+```shell
+$ ./my_test > gtest_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.
+
+
+    ## 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:
+
+```c++
+// 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");
+}
+```
+
+gtest-death-test_test.cc contains more examples if you are interested.
+
+## I have a fixture class `FooTest`, but `TEST_F(FooTest, Bar)` gives me error ``"no matching function for call to `FooTest::FooTest()'"``. Why?
+
+Googletest 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 `FooTest`
+    (`DISALLOW_EVIL_CONSTRUCTORS()` does this), then you need to define a
+    default constructor, even if it would be empty.
+*   If `FooTest` 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 googletest require the entire test case, instead of individual tests, to be named *DeathTest when it uses ASSERT_DEATH?
+
+googletest 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. googletest 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:
+
+```c++
+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 \*DeathTest 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:
+
+```c++
+class FooTest : public ::testing::Test { ... };
+
+TEST_F(FooTest, Abc) { ... }
+TEST_F(FooTest, Def) { ... }
+
+using FooDeathTest = FooTest;
+
+TEST_F(FooDeathTest, Uvw) { ... EXPECT_DEATH(...) ... }
+TEST_F(FooDeathTest, Xyz) { ... ASSERT_DEATH(...) ... }
+```
+
+## googletest prints the LOG messages in a death test's child process only when the test fails. How can I see the LOG messages when the death test succeeds?
+
+Printing the LOG messages generated by the statement inside `EXPECT_DEATH()`
+makes it harder to search for real problems in the parent's log. Therefore,
+googletest only prints them when the death test has failed.
+
+If you really need to see such LOG messages, a workaround is to temporarily
+break the death test (e.g. by changing the regex pattern it is expected to
+match). Admittedly, this is a hack. We'll consider a more permanent solution
+after the fork-and-exec-style death tests are implemented.
+
+## 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. See go/totw/49 for details.
+
+## How do I suppress the memory leak messages on Windows?
+
+Since the statically initialized googletest 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.
+
+
+## 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](https://en.wikipedia.org/wiki/Heisenbug). Therefore we strongly
+advise against the practice, and googletest 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](https://en.wikipedia.org/wiki/Dependency_injection). 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 (the
+[`testonly`](https://docs.bazel.build/versions/master/be/common-definitions.html#common.testonly)
+attribute for BUILD targets helps to ensure that), 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.
+
+
+## How do I temporarily disable a test?
+
+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).
+
+To include disabled tests in test execution, just invoke the test program with
+the --gtest_also_run_disabled_tests flag.
+
+## 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`).
+
+```c++
+namespace foo {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace foo
+
+namespace bar {
+TEST(CoolTest, DoSomething) {
+  SUCCEED();
+}
+}  // namespace bar
+```
+
+However, the following code is **not allowed** and will produce a runtime error
+from googletest because the test methods are using different test fixture
+classes with the same test case name.
+
+```c++
+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 bar
+```

googletest/docs/primer.md

+# Googletest Primer
+
+
+## Introduction: Why googletest?
+
+*googletest* helps you write better C++ tests.
+
+googletest is a testing framework developed by the Testing
+Technology team with Google's specific
+requirements and constraints in mind. No matter whether you work on Linux,
+Windows, or a Mac, if you write C++ code, googletest can help you. And it
+supports *any* kind of tests, not just unit tests.
+
+So what makes a good test, and how does googletest 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. googletest isolates the
+    tests by running each of them on a different object. When a test fails,
+    googletest allows you to run it in isolation for quick debugging.
+1.  Tests should be well *organized* and reflect the structure of the tested
+    code. googletest 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*. Google has a lot of code that is
+    platform-neutral, its tests should also be platform-neutral. googletest
+    works on different OSes, with different compilers (gcc, icc, and MSVC), with
+    or without exceptions, so googletest tests can easily work with a variety of
+    configurations.
+1.  When tests fail, they should provide as much *information* about the problem
+    as possible. googletest 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*. googletest 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 googletest, 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 googletest 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!
+
+## Beware of the nomenclature
+
+_Note:_ There might be some confusion of idea due to different
+definitions of the terms _Test_, _Test Case_ and _Test Suite_, so beware
+of misunderstanding these.
+
+Historically, googletest started to use the term _Test Case_ for grouping
+related tests, whereas current publications including the International Software
+Testing Qualifications Board ([ISTQB](http://www.istqb.org/)) and various
+textbooks on Software Quality use the term _[Test
+Suite](http://glossary.istqb.org/search/test%20suite)_ for this.
+
+The related term _Test_, as it is used in the googletest, is corresponding to
+the term _[Test Case](http://glossary.istqb.org/search/test%20case)_ of ISTQB
+and others.
+
+The term _Test_ is commonly of broad enough sense, including ISTQB's
+definition of _Test Case_, so it's not much of a problem here. But the
+term _Test Case_ as used in Google Test is of contradictory sense and thus confusing.
+
+Unfortunately replacing the term _Test Case_ by _Test Suite_ throughout the
+googletest is not easy without breaking dependent projects, as `TestCase` is
+part of the public API at various places.
+
+So for the time being, please be aware of the different definitions of
+the terms:
+
+Meaning                                                                              | googletest Term                                                                                            | [ISTQB](http://www.istqb.org/) Term
+:----------------------------------------------------------------------------------- | :--------------------------------------------------------------------------------------------------------- | :----------------------------------
+Exercise a particular program path with specific input values and verify the results | [TEST()](#simple-tests)                                                                                    | [Test Case](http://glossary.istqb.org/search/test%20case)
+A set of several tests related to one component                                      | [TestCase](#basic-concepts) | [TestSuite](http://glossary.istqb.org/search/test%20suite)
+
+## Basic Concepts
+
+When using googletest, 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
+
+googletest assertions are macros that resemble function calls. You test a class
+or function by making assertions about its behavior. When an assertion fails,
+googletest 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 googletest'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 failure 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:
+
+```c++
+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(val1, val2);` | `EXPECT_EQ(val1, val2);` | `val1 == val2`
+`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`
+
+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. If
+`<<` is supported, it will be called to print the arguments when the assertion
+fails; otherwise googletest will attempt to print them in the best way it can.
+For more details and how to customize the printing of the arguments, see
+gMock [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). Since this is
+discouraged by the Google [C++ Style
+Guide](https://google.github.io/styleguide/cppguide.html#Operator_Overloading),
+you may need to use `ASSERT_TRUE()` or `EXPECT_TRUE()` to assert the equality of
+two objects of a user-defined type.
+
+However, when possible, `ASSERT_EQ(actual, expected)` is preferred to
+`ASSERT_TRUE(actual == expected)`, since it tells you `actual` and `expected`'s
+values on failure.
+
+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(c_string, NULL)`. Consider use
+`ASSERT_EQ(c_string, nullptr)` if c++11 is supported. To compare two `string`
+objects, you should use `ASSERT_EQ`.
+
+When doing pointer comparisons use `*_EQ(ptr, nullptr)` and `*_NE(ptr, nullptr)`
+instead of `*_EQ(ptr, NULL)` and `*_NE(ptr, NULL)`. This is because `nullptr` is
+typed while `NULL` is not. See [FAQ](faq.md#why-does-google-test-support-expect_eqnull-ptr-and-assert_eqnull-ptr-but-not-expect_nenull-ptr-and-assert_nenull-ptr)
+for more details.
+
+If you're working with floating point numbers, you may want to use the floating
+point variations of some of these macros in order to avoid problems caused by
+rounding. See [Advanced googletest Topics](advanced.md) for details.
+
+Macros in this section work with both narrow and wide string objects (`string`
+and `wstring`).
+
+**Availability**: Linux, Windows, Mac.
+
+**Historical note**: Before February 2016 `*_EQ` had a convention of calling it
+as `ASSERT_EQ(expected, actual)`, so lots of existing code uses this order. Now
+`*_EQ` treats both parameters in the same way.
+
+### 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(str1, str2);`     | `EXPECT_STREQ(str1, str2);`     | the two C strings have the same content                  |
+| `ASSERT_STRNE(str1, str2);`     | `EXPECT_STRNE(str1, str2);`     | the two C strings have different contents                |
+| `ASSERT_STRCASEEQ(str1, str2);` | `EXPECT_STRCASEEQ(str1, str2);` | the two C strings have the same content, ignoring case   |
+| `ASSERT_STRCASENE(str1, str2);` | `EXPECT_STRCASENE(str1, str2);` | the two C strings have different contents, ignoring case |
+
+Note that "CASE" in an assertion name means that case is ignored. A `NULL`
+pointer and an empty string are considered *different*.
+
+`*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.
+
+**Availability**: Linux, Windows, Mac.
+
+**See also**: For more string comparison tricks (substring, prefix, suffix, and
+regular expression matching, for example), see
+[this](https://github.com/google/googletest/blob/master/googletest/docs/advanced.md)
+in the Advanced googletest 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 googletest 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.
+
+```c++
+TEST(TestCaseName, TestName) {
+  ... 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:
+
+```c++
+int Factorial(int n);  // Returns the factorial of n
+```
+
+A test case for this function might look like:
+
+```c++
+// Tests factorial of 0.
+TEST(FactorialTest, HandlesZeroInput) {
+  EXPECT_EQ(Factorial(0), 1);
+}
+
+// Tests factorial of positive numbers.
+TEST(FactorialTest, HandlesPositiveInput) {
+  EXPECT_EQ(Factorial(1), 1);
+  EXPECT_EQ(Factorial(2), 2);
+  EXPECT_EQ(Factorial(3), 6);
+  EXPECT_EQ(Factorial(8), 40320);
+}
+```
+
+googletest 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`.
+
+When naming your test cases and tests, you should follow the same convention as
+for [naming functions and
+classes](https://google.github.io/styleguide/cppguide.html#Function_Names).
+
+**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:
+
+1.  Derive a class from `::testing::Test` . Start its body with `protected:` 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` - Use `override` in C++11 to make sure you
+    spelled it correctly
+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](faq.md#should-i-use-the-constructordestructor-of-the-test-fixture-or-the-set-uptear-down-function) entry.
+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:
+
+```c++
+TEST_F(TestCaseName, TestName) {
+  ... 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()` , googletest will create a *fresh* test
+fixture at runtime, immediately initialize it via `SetUp()` , run the test,
+clean up by calling `TearDown()` , and then delete the test fixture. Note that
+different tests in the same test case have different test fixture objects, and
+googletest always deletes a test fixture before it creates the next one.
+googletest 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:
+
+```c++
+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.
+
+```c++
+class QueueTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+     q1_.Enqueue(1);
+     q2_.Enqueue(2);
+     q2_.Enqueue(3);
+  }
+
+  // void TearDown() override {}
+
+  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.
+
+```c++
+TEST_F(QueueTest, IsEmptyInitially) {
+  EXPECT_EQ(q0_.size(), 0);
+}
+
+TEST_F(QueueTest, DequeueWorks) {
+  int* n = q0_.Dequeue();
+  EXPECT_EQ(n, nullptr);
+
+  n = q1_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 1);
+  EXPECT_EQ(q1_.size(), 0);
+  delete n;
+
+  n = q2_.Dequeue();
+  ASSERT_NE(n, nullptr);
+  EXPECT_EQ(*n, 2);
+  EXPECT_EQ(q2_.size(), 1);
+  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_NE(nullptr, n)=, 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.  googletest 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.
+
+
+## Invoking the Tests
+
+`TEST()` and `TEST_F()` implicitly register their tests with googletest. 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 googletest flags
+
+*   Creates a test fixture object for the first test.
+
+*   Initializes it via `SetUp()`.
+
+*   Runs the test on the fixture object.
+
+*   Cleans up the fixture via `TearDown()`.
+
+*   Deletes the fixture.
+
+* Restores the state of all googletest flags
+
+*   Repeats the above steps for the next test, until all tests have run.
+
+If a fatal failure happens the subsequent steps will be skipped.
+
+> IMPORTANT: You must **not** ignore the return value of `RUN_ALL_TESTS()`, or
+> you will get 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 googletest features (e.g. thread-safe [death
+> tests](advanced#death-tests)) and thus is not supported.
+
+**Availability**: Linux, Windows, Mac.
+
+## Writing the main() Function
+
+In `google3`, the simplest approach is to use the default main() function
+provided by linking in `"//testing/base/public:gtest_main"`. If that doesn't
+cover what you need, you should write your own main() function, which should
+return the value of `RUN_ALL_TESTS()`. Link to `"//testing/base/public:gunit"`.
+You can start from this boilerplate:
+
+```c++
+#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.
+  }
+
+  ~FooTest() override {
+     // 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:
+
+  void SetUp() override {
+     // Code here will be called immediately after the constructor (right
+     // before each test).
+  }
+
+  void TearDown() override {
+     // 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 std::string input_filepath = "this/package/testdata/myinputfile.dat";
+  const std::string output_filepath = "this/package/testdata/myoutputfile.dat";
+  Foo f;
+  EXPECT_EQ(f.Bar(input_filepath, output_filepath), 0);
+}
+
+// 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
+googletest 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](advanced.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.
+
+NOTE: `ParseGUnitFlags()` is deprecated in favor of `InitGoogleTest()`.
+
+
+## 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.

googletest/docs/samples.md

+# Googletest Samples {#samples}
+
+If you're like us, you'd like to look at [googletest
+samples.](https://github.com/google/googletest/tree/master/googletest/samples)
+The sample directory has a number of well-commented samples showing how to use a
+variety of googletest features.
+
+*   Sample #1 shows the basic steps of using googletest to test C++ functions.
+*   Sample #2 shows a more complex unit test for a class with multiple member
+    functions.
+*   Sample #3 uses a test fixture.
+*   Sample #4 teaches you how to use googletest and `googletest.h` together to
+    get the best of both libraries.
+*   Sample #5 puts shared testing logic in a base test fixture, and reuses it in
+    derived fixtures.
+*   Sample #6 demonstrates type-parameterized tests.
+*   Sample #7 teaches the basics of value-parameterized tests.
+*   Sample #8 shows using `Combine()` in value-parameterized tests.
+*   Sample #9 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 shows use of the listener API to implement a primitive memory
+    leak checker.

googletest/include/gtest/gtest-death-test.h

@@ -26,14 +26,14 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 //
-// Author: wan@google.com (Zhanyong Wan)
-//
-// The Google C++ Testing Framework (Google Test)
+// The Google C++ Testing and Mocking Framework (Google Test)
 //
 // This header file defines the public API for death tests.  It is
 // #included by gtest.h so a user doesn't need to include this
 // directly.
+// GOOGLETEST_CM0001 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_GTEST_DEATH_TEST_H_
 #define GTEST_INCLUDE_GTEST_GTEST_DEATH_TEST_H_
@@ -99,6 +99,7 @@ GTEST_API_ bool InDeathTestChild();
 //
 // On the regular expressions used in death tests:
 //
+//   GOOGLETEST_CM0005 DO NOT DELETE
 //   On POSIX-compliant systems (*nix), we use the <regex.h> library,
 //   which uses the POSIX extended regex syntax.
 //
@@ -160,7 +161,7 @@ GTEST_API_ bool InDeathTestChild();
 //   is rarely a problem as people usually don't put the test binary
 //   directory in PATH.
 //
-// TODO(wan@google.com): make thread-safe death tests search the PATH.
+// FIXME: make thread-safe death tests search the PATH.
 
 // Asserts that a given statement causes the program to exit, with an
 // integer exit status that satisfies predicate, and emitting error output
@@ -198,9 +199,10 @@ class GTEST_API_ ExitedWithCode {
   const int exit_code_;
 };
 
-# if !GTEST_OS_WINDOWS
+# if !GTEST_OS_WINDOWS && !GTEST_OS_FUCHSIA
 // Tests that an exit code describes an exit due to termination by a
 // given signal.
+// GOOGLETEST_CM0006 DO NOT DELETE
 class GTEST_API_ KilledBySignal {
  public:
   explicit KilledBySignal(int signum);

googletest/include/gtest/gtest-message.h

@@ -26,10 +26,9 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 //
-// Author: wan@google.com (Zhanyong Wan)
-//
-// The Google C++ Testing Framework (Google Test)
+// The Google C++ Testing and Mocking Framework (Google Test)
 //
 // This header file defines the Message class.
 //
@@ -43,6 +42,8 @@
 // to CHANGE WITHOUT NOTICE.  Therefore DO NOT DEPEND ON IT in a user
 // program!
 
+// GOOGLETEST_CM0001 DO NOT DELETE
+
 #ifndef GTEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
 #define GTEST_INCLUDE_GTEST_GTEST_MESSAGE_H_
 

googletest/include/gtest/gtest-param-test.h

@@ -31,13 +31,12 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-// Authors: vladl@google.com (Vlad Losev)
-//
 // Macros and functions for implementing parameterized tests
-// in Google C++ Testing Framework (Google Test)
+// in Google C++ Testing and Mocking Framework (Google Test)
 //
 // This file is generated by a SCRIPT.  DO NOT EDIT BY HAND!
 //
+// GOOGLETEST_CM0001 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
 #define GTEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
@@ -1371,8 +1370,6 @@ internal::CartesianProductHolder10<Generator1, Generator2, Generator3,
 }
 # endif  // GTEST_HAS_COMBINE
 
-
-
 # define TEST_P(test_case_name, test_name) \
   class GTEST_TEST_CLASS_NAME_(test_case_name, test_name) \
       : public test_case_name { \
@@ -1386,8 +1383,8 @@ internal::CartesianProductHolder10<Generator1, Generator2, Generator3,
               #test_case_name, \
               ::testing::internal::CodeLocation(\
                   __FILE__, __LINE__))->AddTestPattern(\
-                      #test_case_name, \
-                      #test_name, \
+                      GTEST_STRINGIFY_(test_case_name), \
+                      GTEST_STRINGIFY_(test_name), \
                       new ::testing::internal::TestMetaFactory< \
                           GTEST_TEST_CLASS_NAME_(\
                               test_case_name, test_name)>()); \

googletest/include/gtest/gtest-param-test.h.pump

@@ -30,13 +30,12 @@ $var maxtuple = 10  $$ Maximum number of Combine arguments we want to support.
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-// Authors: vladl@google.com (Vlad Losev)
-//
 // Macros and functions for implementing parameterized tests
-// in Google C++ Testing Framework (Google Test)
+// in Google C++ Testing and Mocking Framework (Google Test)
 //
 // This file is generated by a SCRIPT.  DO NOT EDIT BY HAND!
 //
+// GOOGLETEST_CM0001 DO NOT DELETE
 #ifndef GTEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
 #define GTEST_INCLUDE_GTEST_GTEST_PARAM_TEST_H_
 
@@ -436,8 +435,6 @@ internal::CartesianProductHolder$i<$for j, [[Generator$j]]> Combine(
 ]]
 # endif  // GTEST_HAS_COMBINE
 
-
-
 # define TEST_P(test_case_name, test_name) \
   class GTEST_TEST_CLASS_NAME_(test_case_name, test_name) \
       : public test_case_name { \
@@ -451,8 +448,8 @@ internal::CartesianProductHolder$i<$for j, [[Generator$j]]> Combine(
               #test_case_name, \
               ::testing::internal::CodeLocation(\
                   __FILE__, __LINE__))->AddTestPattern(\
-                      #test_case_name, \
-                      #test_name, \
+                      GTEST_STRINGIFY_(test_case_name), \
+                      GTEST_STRINGIFY_(test_name), \
                       new ::testing::internal::TestMetaFactory< \
                           GTEST_TEST_CLASS_NAME_(\
                               test_case_name, test_name)>()); \

googletest/include/gtest/gtest-printers.h

@@ -26,10 +26,9 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// Author: wan@google.com (Zhanyong Wan)
 
-// Google Test - The Google C++ Testing Framework
+
+// Google Test - The Google C++ Testing and Mocking Framework
 //
 // This file implements a universal value printer that can print a
 // value of any type T:
@@ -96,6 +95,8 @@
 // being defined as many user-defined container types don't have
 // value_type.
 
+// GOOGLETEST_CM0001 DO NOT DELETE
+
 #ifndef GTEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
 #define GTEST_INCLUDE_GTEST_GTEST_PRINTERS_H_
 
@@ -112,8 +113,9 @@
 #endif
 
 #if GTEST_HAS_ABSL
-#include "absl/types/optional.h"
 #include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "absl/types/variant.h"
 #endif  // GTEST_HAS_ABSL
 
 namespace testing {
@@ -509,17 +511,19 @@ void PrintTo(const T& value, ::std::ostream* os) {
   // function pointers so that the `*os << p` in the object pointer overload
   // doesn't cause that warning either.
   DefaultPrintTo(
-      WrapPrinterType<
-          (sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) && !IsRecursiveContainer<T>::value
-            ? kPrintContainer : !is_pointer<T>::value
-              ? kPrintOther
+      WrapPrinterType <
+                  (sizeof(IsContainerTest<T>(0)) == sizeof(IsContainer)) &&
+              !IsRecursiveContainer<T>::value
+          ? kPrintContainer
+          : !is_pointer<T>::value
+                ? kPrintOther
 #if GTEST_LANG_CXX11
                 : std::is_function<typename std::remove_pointer<T>::type>::value
 #else
                 : !internal::ImplicitlyConvertible<T, const void*>::value
 #endif
                       ? kPrintFunctionPointer
-                      : kPrintPointer>(),
+                      : kPrintPointer > (),
       value, os);
 }
 
@@ -634,6 +638,10 @@ inline void PrintTo(absl::string_view sp, ::std::ostream* os) {
 }
 #endif  // GTEST_HAS_ABSL
 
+#if GTEST_LANG_CXX11
+inline void PrintTo(std::nullptr_t, ::std::ostream* os) { *os << "(nullptr)"; }
+#endif  // GTEST_LANG_CXX11
+
 #if GTEST_HAS_TR1_TUPLE || GTEST_HAS_STD_TUPLE_
 // Helper function for printing a tuple.  T must be instantiated with
 // a tuple type.
@@ -781,6 +789,28 @@ class UniversalPrinter<::absl::optional<T>> {
   }
 };
 
+// Printer for absl::variant
+
+template <typename... T>
+class UniversalPrinter<::absl::variant<T...>> {
+ public:
+  static void Print(const ::absl::variant<T...>& value, ::std::ostream* os) {
+    *os << '(';
+    absl::visit(Visitor{os}, value);
+    *os << ')';
+  }
+
+ private:
+  struct Visitor {
+    template <typename U>
+    void operator()(const U& u) const {
+      *os << "'" << GetTypeName<U>() << "' with value ";
+      UniversalPrint(u, os);
+    }
+    ::std::ostream* os;
+  };
+};
+
 #endif  // GTEST_HAS_ABSL
 
 // UniversalPrintArray(begin, len, os) prints an array of 'len'
@@ -796,7 +826,7 @@ void UniversalPrintArray(const T* begin, size_t len, ::std::ostream* os) {
     // If the array has more than kThreshold elements, we'll have to
     // omit some details by printing only the first and the last
     // kChunkSize elements.
-    // TODO(wan@google.com): let the user control the threshold using a flag.
+    // FIXME: let the user control the threshold using a flag.
     if (len <= kThreshold) {
       PrintRawArrayTo(begin, len, os);
     } else {

googletest/include/gtest/gtest-spi.h

@@ -26,12 +26,13 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// Author: wan@google.com (Zhanyong Wan)
+
 //
 // Utilities for testing Google Test itself and code that uses Google Test
 // (e.g. frameworks built on top of Google Test).
 
+// GOOGLETEST_CM0004 DO NOT DELETE
+
 #ifndef GTEST_INCLUDE_GTEST_GTEST_SPI_H_
 #define GTEST_INCLUDE_GTEST_GTEST_SPI_H_
 

googletest/include/gtest/gtest-test-part.h

@@ -27,8 +27,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-// Author: mheule@google.com (Markus Heule)
-//
+// GOOGLETEST_CM0001 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_GTEST_TEST_PART_H_
 #define GTEST_INCLUDE_GTEST_GTEST_TEST_PART_H_

googletest/include/gtest/gtest-typed-test.h

@@ -26,8 +26,9 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-//
-// Author: wan@google.com (Zhanyong Wan)
+
+
+// GOOGLETEST_CM0001 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_GTEST_TYPED_TEST_H_
 #define GTEST_INCLUDE_GTEST_GTEST_TYPED_TEST_H_

googletest/include/gtest/gtest.h

@@ -26,10 +26,9 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 //
-// Author: wan@google.com (Zhanyong Wan)
-//
-// The Google C++ Testing Framework (Google Test)
+// The Google C++ Testing and Mocking Framework (Google Test)
 //
 // This header file defines the public API for Google Test.  It should be
 // included by any test program that uses Google Test.
@@ -48,6 +47,8 @@
 // registration from Barthelemy Dagenais' (barthelemy@prologique.com)
 // easyUnit framework.
 
+// GOOGLETEST_CM0001 DO NOT DELETE
+
 #ifndef GTEST_INCLUDE_GTEST_GTEST_H_
 #define GTEST_INCLUDE_GTEST_GTEST_H_
 
@@ -82,6 +83,15 @@
 
 namespace testing {
 
+// Silence C4100 (unreferenced formal parameter) and 4805
+// unsafe mix of type 'const int' and type 'const bool'
+#ifdef _MSC_VER
+# pragma warning(push)
+# pragma warning(disable:4805)
+# pragma warning(disable:4100)
+#endif
+
+
 // Declares the flags.
 
 // This flag temporary enables the disabled tests.
@@ -163,6 +173,7 @@ class TestEventListenersAccessor;
 class TestEventRepeater;
 class UnitTestRecordPropertyTestHelper;
 class WindowsDeathTest;
+class FuchsiaDeathTest;
 class UnitTestImpl* GetUnitTestImpl();
 void ReportFailureInUnknownLocation(TestPartResult::Type result_type,
                                     const std::string& message);
@@ -304,7 +315,7 @@ class GTEST_API_ AssertionResult {
   const char* message() const {
     return message_.get() != NULL ?  message_->c_str() : "";
   }
-  // TODO(vladl@google.com): Remove this after making sure no clients use it.
+  // FIXME: Remove this after making sure no clients use it.
   // Deprecated; please use message() instead.
   const char* failure_message() const { return message(); }
 
@@ -584,6 +595,7 @@ class GTEST_API_ TestResult {
   friend class internal::TestResultAccessor;
   friend class internal::UnitTestImpl;
   friend class internal::WindowsDeathTest;
+  friend class internal::FuchsiaDeathTest;
 
   // Gets the vector of TestPartResults.
   const std::vector<TestPartResult>& test_part_results() const {
@@ -609,7 +621,7 @@ class GTEST_API_ TestResult {
 
   // Adds a failure if the key is a reserved attribute of Google Test
   // testcase tags.  Returns true if the property is valid.
-  // TODO(russr): Validate attribute names are legal and human readable.
+  // FIXME: Validate attribute names are legal and human readable.
   static bool ValidateTestProperty(const std::string& xml_element,
                                    const TestProperty& test_property);
 
@@ -2298,6 +2310,10 @@ bool StaticAssertTypeEq() {
 // Tries to determine an appropriate directory for the platform.
 GTEST_API_ std::string TempDir();
 
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+
 }  // namespace testing
 
 // Use this function in main() to run all tests.  It returns 0 if all

googletest/include/gtest/gtest_pred_impl.h

@@ -32,6 +32,8 @@
 //
 // Implements a family of generic predicate assertion macros.
 
+// GOOGLETEST_CM0001 DO NOT DELETE
+
 #ifndef GTEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
 #define GTEST_INCLUDE_GTEST_GTEST_PRED_IMPL_H_
 

googletest/include/gtest/gtest_prod.h

@@ -26,10 +26,10 @@
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 //
-// Author: wan@google.com (Zhanyong Wan)
-//
-// Google C++ Testing Framework definitions useful in production code.
+// Google C++ Testing and Mocking Framework definitions useful in production code.
+// GOOGLETEST_CM0003 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_GTEST_PROD_H_
 #define GTEST_INCLUDE_GTEST_GTEST_PROD_H_
@@ -40,17 +40,20 @@
 //
 // class MyClass {
 //  private:
-//   void MyMethod();
-//   FRIEND_TEST(MyClassTest, MyMethod);
+//   void PrivateMethod();
+//   FRIEND_TEST(MyClassTest, PrivateMethodWorks);
 // };
 //
 // class MyClassTest : public testing::Test {
 //   // ...
 // };
 //
-// TEST_F(MyClassTest, MyMethod) {
-//   // Can call MyClass::MyMethod() here.
+// TEST_F(MyClassTest, PrivateMethodWorks) {
+//   // Can call MyClass::PrivateMethod() here.
 // }
+//
+// Note: The test class must be in the same namespace as the class being tested.
+// For example, putting MyClassTest in an anonymous namespace will not work.
 
 #define FRIEND_TEST(test_case_name, test_name)\
 friend class test_case_name##_##test_name##_Test

googletest/include/gtest/internal/custom/README.md

+# Customization Points
+
+The custom directory is an injection point for custom user configurations.
+
+## Header `gtest.h`
+
+### The following macros can be defined:
+
+*   `GTEST_OS_STACK_TRACE_GETTER_` - The name of an implementation of
+    `OsStackTraceGetterInterface`.
+*   `GTEST_CUSTOM_TEMPDIR_FUNCTION_` - An override for `testing::TempDir()`. See
+    `testing::TempDir` for semantics and signature.
+
+## Header `gtest-port.h`
+
+The following macros can be defined:
+
+### Flag related macros:
+
+*   `GTEST_FLAG(flag_name)`
+*   `GTEST_USE_OWN_FLAGFILE_FLAG_` - Define to 0 when the system provides its
+    own flagfile flag parsing.
+*   `GTEST_DECLARE_bool_(name)`
+*   `GTEST_DECLARE_int32_(name)`
+*   `GTEST_DECLARE_string_(name)`
+*   `GTEST_DEFINE_bool_(name, default_val, doc)`
+*   `GTEST_DEFINE_int32_(name, default_val, doc)`
+*   `GTEST_DEFINE_string_(name, default_val, doc)`
+
+### Logging:
+
+*   `GTEST_LOG_(severity)`
+*   `GTEST_CHECK_(condition)`
+*   Functions `LogToStderr()` and `FlushInfoLog()` have to be provided too.
+
+### Threading:
+
+*   `GTEST_HAS_NOTIFICATION_` - Enabled if Notification is already provided.
+*   `GTEST_HAS_MUTEX_AND_THREAD_LOCAL_` - Enabled if `Mutex` and `ThreadLocal`
+    are already provided. Must also provide `GTEST_DECLARE_STATIC_MUTEX_(mutex)`
+    and `GTEST_DEFINE_STATIC_MUTEX_(mutex)`
+*   `GTEST_EXCLUSIVE_LOCK_REQUIRED_(locks)`
+*   `GTEST_LOCK_EXCLUDED_(locks)`
+
+### Underlying library support features
+
+*   `GTEST_HAS_CXXABI_H_`
+
+### Exporting API symbols:
+
+*   `GTEST_API_` - Specifier for exported symbols.
+
+## Header `gtest-printers.h`
+
+*   See documentation at `gtest/gtest-printers.h` for details on how to define a
+    custom printer.

googletest/include/gtest/internal/custom/gtest-port.h

@@ -27,45 +27,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-// Injection point for custom user configurations.
-// The following macros can be defined:
-//
-//   Flag related macros:
-//     GTEST_FLAG(flag_name)
-//     GTEST_USE_OWN_FLAGFILE_FLAG_  - Define to 0 when the system provides its
-//                                     own flagfile flag parsing.
-//     GTEST_DECLARE_bool_(name)
-//     GTEST_DECLARE_int32_(name)
-//     GTEST_DECLARE_string_(name)
-//     GTEST_DEFINE_bool_(name, default_val, doc)
-//     GTEST_DEFINE_int32_(name, default_val, doc)
-//     GTEST_DEFINE_string_(name, default_val, doc)
-//
-//   Test filtering:
-//     GTEST_TEST_FILTER_ENV_VAR_ - The name of an environment variable that
-//                                  will be used if --GTEST_FLAG(test_filter)
-//                                  is not provided.
-//
-//   Logging:
-//     GTEST_LOG_(severity)
-//     GTEST_CHECK_(condition)
-//     Functions LogToStderr() and FlushInfoLog() have to be provided too.
-//
-//   Threading:
-//     GTEST_HAS_NOTIFICATION_ - Enabled if Notification is already provided.
-//     GTEST_HAS_MUTEX_AND_THREAD_LOCAL_ - Enabled if Mutex and ThreadLocal are
-//                                         already provided.
-//     Must also provide GTEST_DECLARE_STATIC_MUTEX_(mutex) and
-//     GTEST_DEFINE_STATIC_MUTEX_(mutex)
-//
-//     GTEST_EXCLUSIVE_LOCK_REQUIRED_(locks)
-//     GTEST_LOCK_EXCLUDED_(locks)
-//
-//   Underlying library support features:
-//     GTEST_HAS_CXXABI_H_
-//
-//   Exporting API symbols:
-//     GTEST_API_ - Specifier for exported symbols.
+// Injection point for custom user configurations. See README for details
 //
 // ** Custom implementation starts here **
 

googletest/include/gtest/internal/custom/gtest-printers.h

@@ -31,8 +31,8 @@
 // installation of gTest.
 // It will be included from gtest-printers.h and the overrides in this file
 // will be visible to everyone.
-// See documentation at gtest/gtest-printers.h for details on how to define a
-// custom printer.
+//
+// Injection point for custom user configurations. See README for details
 //
 // ** Custom implementation starts here **
 

googletest/include/gtest/internal/custom/gtest.h

@@ -27,15 +27,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-// Injection point for custom user configurations.
-// The following macros can be defined:
-//
-// GTEST_OS_STACK_TRACE_GETTER_  - The name of an implementation of
-//                                 OsStackTraceGetterInterface.
-//
-// GTEST_CUSTOM_TEMPDIR_FUNCTION_ - An override for testing::TempDir().
-//                                  See testing::TempDir for semantics and
-//                                  signature.
+// Injection point for custom user configurations. See README for details
 //
 // ** Custom implementation starts here **
 

googletest/include/gtest/internal/gtest-death-test-internal.h

@@ -27,11 +27,11 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 //
-//
-// The Google C++ Testing Framework (Google Test)
+// The Google C++ Testing and Mocking Framework (Google Test)
 //
 // This header file defines internal utilities needed for implementing
 // death tests.  They are subject to change without notice.
+// GOOGLETEST_CM0001 DO NOT DELETE
 
 #ifndef GTEST_INCLUDE_GTEST_INTERNAL_GTEST_DEATH_TEST_INTERNAL_H_
 #define GTEST_INCLUDE_GTEST_INTERNAL_GTEST_DEATH_TEST_INTERNAL_H_
@@ -217,14 +217,18 @@ GTEST_API_ bool ExitedUnsuccessfully(int exit_status);
 // can be streamed.
 
 // This macro is for implementing ASSERT/EXPECT_DEBUG_DEATH when compiled in
-// NDEBUG mode. In this case we need the statements to be executed, the regex is
-// ignored, and the macro must accept a streamed message even though the message
-// is never printed.
-# define GTEST_EXECUTE_STATEMENT_(statement, regex) \
-  GTEST_AMBIGUOUS_ELSE_BLOCKER_ \
-  if (::testing::internal::AlwaysTrue()) { \
-     GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
-  } else \
+// NDEBUG mode. In this case we need the statements to be executed and the macro
+// must accept a streamed message even though the message is never printed.
+// The regex object is not evaluated, but it is used to prevent "unused"
+// warnings and to avoid an expression that doesn't compile in debug mode.
+#define GTEST_EXECUTE_STATEMENT_(statement, regex)             \
+  GTEST_AMBIGUOUS_ELSE_BLOCKER_                                \
+  if (::testing::internal::AlwaysTrue()) {                     \
+    GTEST_SUPPRESS_UNREACHABLE_CODE_WARNING_BELOW_(statement); \
+  } else if (!::testing::internal::AlwaysTrue()) {             \
+    const ::testing::internal::RE& gtest_regex = (regex);      \
+    static_cast<void>(gtest_regex);                            \
+  } else                                                       \
     ::testing::Message()
 
 // A class representing the parsed contents of the