python: What am I doing wrong here in my testing code?

I want to understand what I'm doing here wrong.

from enum import Enum, auto
class colors(Enum):
    red= auto()
    green= auto()
    yellow= auto()

This is my class.

     def is_first(self):
        return self is not colors.red

My first function.

    def second(self):
        if self is colors.red:
            return ''
        elif self is green:
            return 'second_type'
        elif self is yellow:
            return 'third_type'

What am I doing wrong in testing I need to them all pass.

     @pytest.mark.parametrize('input_str, expected_result',
                    [('aa', False)])

    def test_is_first(input_str, expected_result):
        assert is_first(input_str) is expected_result

and for my second function

    @pytest.mark.parametrize('input_str, expected_result',
                    [('', True),
            ('second_type', True),
            ('third_type', 'True'),
            ('aa', False)])

    def test_second(input_str, expected_result):
        assert second(input_str) is expected_result