def test_is_none_1(self):
     self.assertIsNone(vowel_shift(None, 0))
 def test_equal_1(self):
     self.assertEqual(vowel_shift('', 0), '')
 def test_equal_9(self):
     self.assertEqual(vowel_shift('AEIOUaeiou', 1), 'uAEIOUaeio')
 def test_equal_8(self):
     self.assertEqual(vowel_shift('Brrrr', 99), 'Brrrr')
 def test_equal_7(self):
     self.assertEqual(vowel_shift('This is a test!', -5), 'This as e tist!')
 def test_equal_5(self):
     self.assertEqual(vowel_shift('This is a test!', 4), 'This is a test!')
 def test_equal_3(self):
     self.assertEqual(vowel_shift('This is a test!', 1), 'Thes is i tast!')