parametrize method with passing and expected failing in pytest without skipping-CodePudding

I want to test a Python function via Pytest. With the parametrize decorator I pass 2 expected passing and one expecting failing (via ValueError in the method).


@pytest.mark.parametrize("input_nr, expected", [
    (123.456, (123, 456)),
    (456.789, (456, 789)),
    pytest.param("123.123", (123, 123),  marks=pytest.mark.xfail(raises=ValueError, strict=True))]
                         )
def test_my_func(input_nr, expected):
    res = my_func(input_nr)
    print("\n"   str(res))
    assert res == expected

From the docs of pytest, I think to understod it right, I have to use pytest.param for adding expected failing tests.

But if I run this in pytest, only the two passing runs are passed and the expected failing run was skipped/ignored.

What do I have to change in parametrize to fail successfully?

CodePudding user response：

xfail will not report a pass. So my test report won't be showing the expected result I hoped for.

So my way will be to handle expected expection in the test code, not via parametrize.

CodePudding user response：

If you want to test your function to fail for specific inputs then write a function that tests exactly those cases separately.

I needed to assume what your my_func does, but it could look something like this:

import pytest


def my_func(num: float):
    if not isinstance(num, float):
        raise ValueError("Wrong format")
    return tuple([int(n) for n in str(num).split(".")])

@pytest.mark.parametrize("input_nr, expected", [
    (123.456, (123, 456)),
    (456.789, (456, 789))
]
                         )
def test_my_func_valid(input_nr, expected):
    """Test function for valid input"""
    res = my_func(input_nr)
    print("\n"   str(res))
    assert res == expected


@pytest.mark.parametrize("input_nr, expected", [("123.123", (123, 123))])
def test_my_func_invalid(input_nr, expected):
    """Test if a ValueError is thrown"""
    with pytest.raises(ValueError) as e:
        my_func(input_nr)

    assert str(e.value) == "Wrong format"