examples/pytest/test_in_list.py
def get_list():
    return ["monkey", "cat"]

def test_in_list():
    assert "dog" in get_list()

$ pytest test_in_list.py

    def test_in_list():
>       assert "dog" in get_list()
E       AssertionError: assert 'dog' in ['monkey', 'cat']
E        +  where ['monkey', 'cat'] = get_list()