Refactor GTZAN unittest (#1148)

Co-authored-by: krishnakalyan3 <skalyan@cloudera.com>

test/torchaudio_unittest/datasets/gtzan_test.py

@@ -12,22 +12,19 @@ from torchaudio_unittest.common_utils import (
 )
 
 
-class TestGTZAN(TempDirMixin, TorchaudioTestCase):
-    backend = 'default'
-
-    root_dir = None
-    samples = []
-    training = []
-    validation = []
-    testing = []
-
-    @classmethod
-    def setUpClass(cls):
-        cls.root_dir = cls.get_base_temp_dir()
+def get_mock_dataset(root_dir):
+    """
+    root_dir: directory to the mocked dataset
+    """
+    mocked_samples = []
+    mocked_training = []
+    mocked_validation = []
+    mocked_testing = []
     sample_rate = 22050
+
     seed = 0
     for genre in gtzan.gtzan_genres:
-            base_dir = os.path.join(cls.root_dir, 'genres', genre)
+        base_dir = os.path.join(root_dir, 'genres', genre)
         os.makedirs(base_dir, exist_ok=True)
         for i in range(100):
             filename = f'{genre}.{i:05d}'
@@ -35,14 +32,34 @@ class TestGTZAN(TempDirMixin, TorchaudioTestCase):
             data = get_whitenoise(sample_rate=sample_rate, duration=0.01, n_channels=1, dtype='int16', seed=seed)
             save_wav(path, data, sample_rate)
             sample = (normalize_wav(data), sample_rate, genre)
-                cls.samples.append(sample)
+            mocked_samples.append(sample)
             if filename in gtzan.filtered_test:
-                    cls.testing.append(sample)
+                mocked_testing.append(sample)
             if filename in gtzan.filtered_train:
-                    cls.training.append(sample)
+                mocked_training.append(sample)
             if filename in gtzan.filtered_valid:
-                    cls.validation.append(sample)
+                mocked_validation.append(sample)
             seed += 1
+    return (mocked_samples, mocked_training, mocked_validation, mocked_testing)
+
+
+class TestGTZAN(TempDirMixin, TorchaudioTestCase):
+    backend = 'default'
+
+    root_dir = None
+    samples = []
+    training = []
+    validation = []
+    testing = []
+
+    @classmethod
+    def setUpClass(cls):
+        cls.root_dir = cls.get_base_temp_dir()
+        mocked_data = get_mock_dataset(cls.root_dir)
+        cls.samples = mocked_data[0]
+        cls.training = mocked_data[1]
+        cls.validation = mocked_data[2]
+        cls.testing = mocked_data[3]
 
     def test_no_subset(self):
         dataset = gtzan.GTZAN(self.root_dir)