def test_empty_ids(self): self.assertEqual(get_single_mismatch_index('', ''), -1)
def test_multiple_differences_index_in_middle(self): self.assertEqual(get_single_mismatch_index('aaaa', 'abba'), -1)
def test_multiple_differences_index_at_end(self): self.assertEqual(get_single_mismatch_index('aaaa', 'aabb'), -1)
def test_one_difference_end(self): self.assertEqual(get_single_mismatch_index('aaaa', 'aaab'), 3)
def test_one_difference_middle(self): self.assertEqual(get_single_mismatch_index('aaaa', 'aaba'), 2)
def test_one_difference_start(self): self.assertEqual(get_single_mismatch_index('aaaa', 'baaa'), 0)
def test_identical_ids(self): self.assertEqual(get_single_mismatch_index('aaa', 'aaa'), -1)
def test_one_character_ids(self): self.assertEqual(get_single_mismatch_index('a', 'a'), -1)