@pytest.mark.parametrize('dayfirst,expected', [(True, '%d/%m/%Y'), (False, '%m/%d/%Y')])
def test_guess_datetime_format_with_dayfirst(dayfirst, expected):
    ambiguous_string = '01/01/2011'
    result = parsing._guess_datetime_format(ambiguous_string, dayfirst=dayfirst)
    assert (result == expected)
@pytest.mark.parametrize('dayfirst,expected', [(True, '%d/%m/%Y'), (False, '%m/%d/%Y')])
def test_guess_datetime_format_with_dayfirst(dayfirst, expected):
    ambiguous_string = '01/01/2011'
    result = parsing._guess_datetime_format(ambiguous_string, dayfirst=dayfirst)
    assert (result == expected)