def test_example(self): self.assertEqual(longest_palindrome('4123215'), '12321')
def test_all_odd(self): self.assertEqual(longest_palindrome('aba'), 'aba')
def test_base1(self): self.assertEqual(longest_palindrome('1'), '1')
def test_all_even(self): self.assertEqual(longest_palindrome('aa'), 'aa')
def test_base0(self): self.assertEqual(longest_palindrome(''), '')