def test_equal_1(self): self.assertEqual(common_ground( 'eat chicken', 'eat chicken and rice' ), 'eat chicken')
def test_equal_9(self): self.assertEqual(common_ground('', 'cc dd'), 'death')
def test_equal_10(self): self.assertEqual(common_ground('', ''), 'death')
def test_equal_8(self): self.assertEqual(common_ground('aa bb', ''), 'death')
def test_equal_6(self): self.assertEqual(common_ground('aa bb cc', 'bb cc bb aa'), 'bb cc aa')
def test_equal_5(self): self.assertEqual(common_ground('aa bb cc', 'bb cc'), 'bb cc')
def test_equal_3(self): self.assertEqual(common_ground( 'i like turtles', 'what are you talking about' ), 'death')
def test_equal_2(self): self.assertEqual(common_ground( 'eat a burger and drink a coke', 'drink a coke' ), 'drink a coke')