def test_empty_string():
assert longest_palindrome('') == 0
def test_single_char():
assert longest_palindrome('a') == 1
def test_long_palindrome_inside_the_string():
assert longest_palindrome('baablkj12345432133d') == 9
def test_no_palindrome():
assert longest_palindrome('abcdefghba') == 1
def test_palindrome_at_the_start_of_the_string():
assert longest_palindrome('aab') == 2
def test_palindrome_at_the_end_of_the_string():
assert longest_palindrome('baa') == 2
def test_two_equal_chars():
assert longest_palindrome('aa') == 2