def test_gcd_of_two_integers_returns_the_right_output(self):
     self.assertTrue(gcd(10, 20) == 10)
     self.assertTrue(gcd(12, 20) == 4)
     self.assertTrue(gcd(5, 7) == 1)
     self.assertTrue(gcd(36, 100) == 4)
 def test_gcd_of_two_integers_returns_the_other_integer_if_one_of_the_integer_is_zero(self):
     self.assertTrue(gcd(0, 1) == 1)
     self.assertEqual(gcd(0, 0), 0)