Port tests in test_transforms_video.py to pytest (#4040)

test/test_transforms_video.py

 import torch
 from torchvision.transforms import Compose
-import unittest
+import pytest
 import random
 import numpy as np
 import warnings
@@ -17,7 +17,7 @@ with warnings.catch_warnings(record=True):
     import torchvision.transforms._transforms_video as transforms
 
 
-class TestVideoTransforms(unittest.TestCase):
+class TestVideoTransforms():
 
     def test_random_crop_video(self):
         numFrames = random.randint(4, 128)
@@ -30,8 +30,8 @@ class TestVideoTransforms(unittest.TestCase):
             transforms.ToTensorVideo(),
             transforms.RandomCropVideo((oheight, owidth)),
         ])(clip)
-        self.assertEqual(result.size(2), oheight)
-        self.assertEqual(result.size(3), owidth)
+        assert result.size(2) == oheight
+        assert result.size(3) == owidth
 
         transforms.RandomCropVideo((oheight, owidth)).__repr__()
 
@@ -46,8 +46,8 @@ class TestVideoTransforms(unittest.TestCase):
             transforms.ToTensorVideo(),
             transforms.RandomResizedCropVideo((oheight, owidth)),
         ])(clip)
-        self.assertEqual(result.size(2), oheight)
-        self.assertEqual(result.size(3), owidth)
+        assert result.size(2) == oheight
+        assert result.size(3) == owidth
 
         transforms.RandomResizedCropVideo((oheight, owidth)).__repr__()
 
@@ -70,7 +70,7 @@ class TestVideoTransforms(unittest.TestCase):
 
         msg = "height: " + str(height) + " width: " \
             + str(width) + " oheight: " + str(oheight) + " owidth: " + str(owidth)
-        self.assertEqual(result.sum().item(), 0, msg)
+        assert result.sum().item() == 0, msg
 
         oheight += 1
         owidth += 1
@@ -82,7 +82,7 @@ class TestVideoTransforms(unittest.TestCase):
 
         msg = "height: " + str(height) + " width: " \
             + str(width) + " oheight: " + str(oheight) + " owidth: " + str(owidth)
-        self.assertEqual(sum1.item() > 1, True, msg)
+        assert sum1.item() > 1, msg
 
         oheight += 1
         owidth += 1
@@ -94,18 +94,19 @@ class TestVideoTransforms(unittest.TestCase):
 
         msg = "height: " + str(height) + " width: " \
             + str(width) + " oheight: " + str(oheight) + " owidth: " + str(owidth)
-        self.assertTrue(sum2.item() > 1, msg)
-        self.assertTrue(sum2.item() > sum1.item(), msg)
+        assert sum2.item() > 1, msg
+        assert sum2.item() > sum1.item(), msg
 
-    @unittest.skipIf(stats is None, 'scipy.stats is not available')
-    def test_normalize_video(self):
+    @pytest.mark.skipif(stats is None, reason='scipy.stats is not available')
+    @pytest.mark.parametrize('channels', [1, 3])
+    def test_normalize_video(self, channels):
         def samples_from_standard_normal(tensor):
             p_value = stats.kstest(list(tensor.view(-1)), 'norm', args=(0, 1)).pvalue
             return p_value > 0.0001
 
         random_state = random.getstate()
         random.seed(42)
-        for channels in [1, 3]:
+
         numFrames = random.randint(4, 128)
         height = random.randint(32, 256)
         width = random.randint(32, 256)
@@ -115,7 +116,7 @@ class TestVideoTransforms(unittest.TestCase):
         mean = [clip[c].mean().item() for c in range(channels)]
         std = [clip[c].std().item() for c in range(channels)]
         normalized = transforms.NormalizeVideo(mean, std)(clip)
-            self.assertTrue(samples_from_standard_normal(normalized))
+        assert samples_from_standard_normal(normalized)
         random.setstate(random_state)
 
         # Checking the optional in-place behaviour
@@ -129,11 +130,11 @@ class TestVideoTransforms(unittest.TestCase):
         numFrames, height, width = 64, 4, 4
         trans = transforms.ToTensorVideo()
 
-        with self.assertRaises(TypeError):
+        with pytest.raises(TypeError):
             trans(np.random.rand(numFrames, height, width, 1).tolist())
             trans(torch.rand((numFrames, height, width, 1), dtype=torch.float))
 
-        with self.assertRaises(ValueError):
+        with pytest.raises(ValueError):
             trans(torch.ones((3, numFrames, height, width, 3), dtype=torch.uint8))
             trans(torch.ones((height, width, 3), dtype=torch.uint8))
             trans(torch.ones((width, 3), dtype=torch.uint8))
@@ -141,7 +142,7 @@ class TestVideoTransforms(unittest.TestCase):
 
         trans.__repr__()
 
-    @unittest.skipIf(stats is None, 'scipy.stats not available')
+    @pytest.mark.skipif(stats is None, reason='scipy.stats not available')
     def test_random_horizontal_flip_video(self):
         random_state = random.getstate()
         random.seed(42)
@@ -157,7 +158,7 @@ class TestVideoTransforms(unittest.TestCase):
 
         p_value = stats.binom_test(num_horizontal, num_samples, p=0.5)
         random.setstate(random_state)
-        self.assertGreater(p_value, 0.0001)
+        assert p_value > 0.0001
 
         num_samples = 250
         num_horizontal = 0
@@ -168,10 +169,10 @@ class TestVideoTransforms(unittest.TestCase):
 
         p_value = stats.binom_test(num_horizontal, num_samples, p=0.7)
         random.setstate(random_state)
-        self.assertGreater(p_value, 0.0001)
+        assert p_value > 0.0001
 
         transforms.RandomHorizontalFlipVideo().__repr__()
 
 
 if __name__ == '__main__':
-    unittest.main()
+    pytest.main([__file__])