Port test_internet.py to pytest and add pytest-mock dependency (#4032)

.circleci/unittest/linux/scripts/environment.yml

@@ -6,6 +6,7 @@ channels:
 dependencies:
   - pytest
   - pytest-cov
+  - pytest-mock
   - pip
   - libpng
   # NOTE: Pinned to fix issues with size_t on Windows

.circleci/unittest/windows/scripts/environment.yml

@@ -6,6 +6,7 @@ channels:
 dependencies:
   - pytest
   - pytest-cov
+  - pytest-mock
   - pip
   - libpng
   # NOTE: Pinned to fix issues with size_t on Windows

CONTRIBUTING.md

@@ -49,7 +49,7 @@ python setup.py develop
 # MACOSX_DEPLOYMENT_TARGET=10.9 CC=clang CXX=clang++ python setup.py develop
 # for C++ debugging, please use DEBUG=1
 # DEBUG=1 python setup.py develop
-pip install flake8 typing mypy pytest scipy
+pip install flake8 typing mypy pytest pytest-mock scipy
 ```
 You may also have to install `libpng-dev` and `libjpeg-turbo8-dev` libraries:
 ```bash

test/test_internet.py

@@ -6,8 +6,7 @@ cleanly ignored in FB internal test infra.
 """
 
 import os
-import unittest
-import unittest.mock
+import pytest
 import warnings
 from urllib.error import URLError
 
@@ -15,7 +14,7 @@ import torchvision.datasets.utils as utils
 from common_utils import get_tmp_dir
 
 
-class DatasetUtilsTester(unittest.TestCase):
+class TestDatasetUtils:
 
     def test_get_redirect_url(self):
         url = "http://www.vision.caltech.edu/visipedia-data/CUB-200-2011/CUB_200_2011.tgz"
@@ -26,7 +25,7 @@ class DatasetUtilsTester(unittest.TestCase):
 
     def test_get_redirect_url_max_hops_exceeded(self):
         url = "http://www.vision.caltech.edu/visipedia-data/CUB-200-2011/CUB_200_2011.tgz"
-        with self.assertRaises(RecursionError):
+        with pytest.raises(RecursionError):
             utils._get_redirect_url(url, max_hops=0)
 
     def test_download_url(self):
@@ -34,38 +33,38 @@ class DatasetUtilsTester(unittest.TestCase):
             url = "http://github.com/pytorch/vision/archive/master.zip"
             try:
                 utils.download_url(url, temp_dir)
-                self.assertFalse(len(os.listdir(temp_dir)) == 0)
+                assert len(os.listdir(temp_dir)) != 0
             except URLError:
-                msg = "could not download test file '{}'".format(url)
-                warnings.warn(msg, RuntimeWarning)
-                raise unittest.SkipTest(msg)
+                pytest.skip(f"could not download test file '{url}'")
 
     def test_download_url_retry_http(self):
         with get_tmp_dir() as temp_dir:
             url = "https://github.com/pytorch/vision/archive/master.zip"
             try:
                 utils.download_url(url, temp_dir)
-                self.assertFalse(len(os.listdir(temp_dir)) == 0)
+                assert len(os.listdir(temp_dir)) != 0
             except URLError:
-                msg = "could not download test file '{}'".format(url)
-                warnings.warn(msg, RuntimeWarning)
-                raise unittest.SkipTest(msg)
+                pytest.skip(f"could not download test file '{url}'")
 
     def test_download_url_dont_exist(self):
         with get_tmp_dir() as temp_dir:
             url = "http://github.com/pytorch/vision/archive/this_doesnt_exist.zip"
-            with self.assertRaises(URLError):
+            with pytest.raises(URLError):
                 utils.download_url(url, temp_dir)
 
-    @unittest.mock.patch("torchvision.datasets.utils.download_file_from_google_drive")
-    def test_download_url_dispatch_download_from_google_drive(self, mock):
+    def test_download_url_dispatch_download_from_google_drive(self, mocker):
         url = "https://drive.google.com/file/d/1hbzc_P1FuxMkcabkgn9ZKinBwW683j45/view"
 
         id = "1hbzc_P1FuxMkcabkgn9ZKinBwW683j45"
         filename = "filename"
         md5 = "md5"
 
+        mocked = mocker.patch('torchvision.datasets.utils.download_file_from_google_drive')
         with get_tmp_dir() as root:
             utils.download_url(url, root, filename, md5)
 
-        mock.assert_called_once_with(id, root, filename, md5)
+        mocked.assert_called_once_with(id, root, filename, md5)
+
+
+if __name__ == '__main__':
+    pytest.main([__file__])