added docstring in unit tests

tests/test_flip_image.py

@@ -7,7 +7,7 @@ from csst_proto.top_level_interface import flip_image, read_test_image
 
 class FlipImageTestCase(unittest.TestCase):
     def test_flip_image(self):
-        # flip test image
+        """ test flip image """
         self.assertTrue(
             np.all(flip_image(read_test_image()) == np.array([[4, 3], [2, 1]]))
         )

tests/test_other_functions.py

@@ -4,6 +4,7 @@ from csst_proto.top_level_interface import a_demo_function
 
 
 class TestCaseDemoFunction(unittest.TestCase):
+    """ test demo function """
     def test_demo_function(self):
         # flip test image
         self.assertTrue(