def test_isint_returns_False_for_strings(x): assert not isint(x)
def test_isint_returns_True_for_real_numbers(x): assert isint(x)
def test_isint_returns_False_for_strings_example(): assert not isint('45') assert not isint('invalid')
def test_isint_returns_True_for_real_numbers_example(): assert isint(-45) assert isint(45)