test: convert to pytest

Instead of built-in `unittest`, now use `pytest`. Find versions that work, convert tests.

ref: N25B-168

test/unit/test_time_block.py

@@ -1,4 +1,4 @@
-import unittest
+import time
 
 import mock
 
@@ -10,31 +10,28 @@ class AnyFloat(object):
         return isinstance(other, float)
 
 
-class TestTimeBlock(unittest.TestCase):
-    def test_no_limit(self):
-        callback = mock.Mock()
+def test_no_limit():
+    callback = mock.Mock()
 
-        with TimeBlock(callback):
-            pass
+    with TimeBlock(callback):
+        pass
 
-        callback.assert_called_once_with(AnyFloat())
-
-    def test_exceed_limit(self):
-        callback = mock.Mock()
-
-        with TimeBlock(callback, 0):
-            pass
-
-        callback.assert_called_once_with(AnyFloat())
-
-    def test_within_limit(self):
-        callback = mock.Mock()
-
-        with TimeBlock(callback, 5):
-            pass
-
-        callback.assert_not_called()
+    callback.assert_called_once_with(AnyFloat())
 
 
-if __name__ == '__main__':
-    unittest.main()
+def test_exceed_limit():
+    callback = mock.Mock()
+
+    with TimeBlock(callback, 0):
+        time.sleep(0.001)
+
+    callback.assert_called_once_with(AnyFloat())
+
+
+def test_within_limit():
+    callback = mock.Mock()
+
+    with TimeBlock(callback, 5):
+        pass
+
+    callback.assert_not_called()