Inherited staticmethod test cases fail

[un-def]

I'm not sure if this is a bug or an expected behavior, but test methods inherited from a parent test class fail if they are staticmethods. This does not happen with regular methods.

An example to reproduce:

@pytest.fixture
def a():
    return 1


@pytest.fixture
def b():
    return 2


class TestBase:

    def test_base(self, a, b):
        assert a + b == 3

    @staticmethod
    def test_base_static(a, b):
        assert a + b == 3


class TestChild(TestBase):

    def test_child(self, a, b):
        assert a + b == 3


    @staticmethod
    def test_child_static(a, b):
        assert a + b == 3

Test session output:

$ pytest -v

platform linux -- Python 3.9.0, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
<...>
collected 6 items                                                                                                     

TestBase::test_base PASSED                                                [ 16%]
TestBase::test_base_static PASSED                                         [ 33%]
TestChild::test_base PASSED                                               [ 50%]
TestChild::test_base_static FAILED                                        [ 66%]
TestChild::test_child PASSED                                              [ 83%]
TestChild::test_child_static PASSED                                       [100%]
<...>
pyfuncitem = <Function test_base_static>

    @hookimpl(trylast=True)
    def pytest_pyfunc_call(pyfuncitem: "Function") -> Optional[object]:
        testfunction = pyfuncitem.obj
        if is_async_function(testfunction):
            async_warn_and_skip(pyfuncitem.nodeid)
        funcargs = pyfuncitem.funcargs
        testargs = {arg: funcargs[arg] for arg in pyfuncitem._fixtureinfo.argnames}
>       result = testfunction(**testargs)
E       TypeError: test_base_static() missing 1 required positional argument: 'a'

.../python3.9/site-packages/_pytest/python.py:184: TypeError

FAILED TestChild::test_base_static - TypeError: test_base_static() missing 1 required positional argument: 'a'

I checked testargs, and the value is {'a': 1, 'b': 2} (as expected) for every test item except for TestChild::test_base_static where it is {'b': 2}.

I suspected this isinstance check, but when I replaced cls.__dict__.get(name, None) with getattr(cls, name, None), it got even worse.

---

$ pip list
Package    Version Location
---------- ------- ------------------------
attrs      20.3.0
iniconfig  1.1.1
packaging  20.4
pip        20.1.1
pluggy     0.13.1
py         1.9.0
pyparsing  2.4.7
pytest     6.1.2
setuptools 46.4.0
six        1.15.0
toml       0.10.2
wheel      0.34.2

$ pytest --version
pytest 6.1.2

$ grep -P '^(VERSION|NAME)=' /etc/os-release
NAME="Ubuntu"
VERSION="20.04.1 LTS (Focal Fossa)"

[RonnyPfannschmidt]

@un-def you found the correct place for the error, but its indeed incorrect to do the lookup via getattr, instead the mro has to be walked as well

i beleive pytest ought to consider looking that metadata up differently as we walk the mro in multiple places now to figure this out