Port test_hub.py to pytest (#4038)

.circleci/config.yml

@@ -242,6 +242,7 @@ jobs:
             pip install --user --progress-bar off --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html
             # need to install torchvision dependencies due to transitive imports
             pip install --user --progress-bar off --editable .
+            pip install pytest
             python test/test_hub.py
 
   torch_onnx_test:

.circleci/config.yml.in

@@ -242,6 +242,7 @@ jobs:
             pip install --user --progress-bar off --pre torch -f https://download.pytorch.org/whl/nightly/cpu/torch_nightly.html
             # need to install torchvision dependencies due to transitive imports
             pip install --user --progress-bar off --editable .
+            pip install pytest
             python test/test_hub.py
 
   torch_onnx_test:

test/test_hub.py

@@ -3,7 +3,7 @@ import tempfile
 import shutil
 import os
 import sys
-import unittest
+import pytest
 
 
 def sum_of_model_parameters(model):
@@ -16,9 +16,9 @@ def sum_of_model_parameters(model):
 SUM_OF_PRETRAINED_RESNET18_PARAMS = -12703.9931640625
 
 
-@unittest.skipIf('torchvision' in sys.modules,
-                 'TestHub must start without torchvision imported')
-class TestHub(unittest.TestCase):
+@pytest.mark.skipif('torchvision' in sys.modules,
+                    reason='TestHub must start without torchvision imported')
+class TestHub:
     # Only run this check ONCE before all tests start.
     # - If torchvision is imported before all tests start, e.g. we might find _C.so
     #   which doesn't exist in downloaded zip but in the installed wheel.
@@ -31,9 +31,7 @@ class TestHub(unittest.TestCase):
             'resnet18',
             pretrained=True,
             progress=False)
-        self.assertAlmostEqual(sum_of_model_parameters(hub_model).item(),
-                               SUM_OF_PRETRAINED_RESNET18_PARAMS,
-                               places=2)
+        assert sum_of_model_parameters(hub_model).item() == pytest.approx(SUM_OF_PRETRAINED_RESNET18_PARAMS)
 
     def test_set_dir(self):
         temp_dir = tempfile.gettempdir()
@@ -43,16 +41,14 @@ class TestHub(unittest.TestCase):
             'resnet18',
             pretrained=True,
             progress=False)
-        self.assertAlmostEqual(sum_of_model_parameters(hub_model).item(),
-                               SUM_OF_PRETRAINED_RESNET18_PARAMS,
-                               places=2)
-        self.assertTrue(os.path.exists(temp_dir + '/pytorch_vision_master'))
+        assert sum_of_model_parameters(hub_model).item() == pytest.approx(SUM_OF_PRETRAINED_RESNET18_PARAMS)
+        assert os.path.exists(temp_dir + '/pytorch_vision_master')
         shutil.rmtree(temp_dir + '/pytorch_vision_master')
 
     def test_list_entrypoints(self):
         entry_lists = hub.list('pytorch/vision', force_reload=True)
-        self.assertIn('resnet18', entry_lists)
+        assert 'resnet18' in entry_lists
 
 
 if __name__ == "__main__":
-    unittest.main()
+    pytest.main([__file__])