pytest 4.2.0 unittest.TestCase can no longer access parent instance

[westhomas]

In pytest==4.1.1 and earlier, unittest.TestCase functions could access their parent class instance. In pytest==4.2.0 the behavior changed.

Was this intended? This causes some problems on my end if so and I'm looking for a work-around going foward.

# test_foo.py
import unittest


class Test:
    def test_method(self):
        pass

def test_function():
    pass


class Broken(unittest.TestCase):
    def test_method(self):
        pass

# conftest.py
def pytest_runtest_makereport(item, call):
    if call.when == 'call':
        print(item.nodeid, 'obj self:', getattr(item.obj, '__self__', None))

$ pip install pytest==4.1.1
$ pytest -q
testing/test_foo.py::Test::test_method obj self: <test_foo.Test object at 0x7f8d1d337518>
.testing/test_foo.py::test_function obj self: None
.testing/test_foo.py::Broken::test_method obj self: test_method (test_foo.Broken)
.                                                                                                                                                                                                                                  [100%]
3 passed in 0.05 seconds

$ pip install pytest==4.2.0
$ pytest -q
testing/test_foo.py::Test::test_method obj self: <test_foo.Test object at 0x7fc6de6aff28>
.testing/test_foo.py::test_function obj self: None
.testing/test_foo.py::Broken::test_method obj self: None .     <======== this is None!
.                                                                                                                                                                                                                                  [100%]
3 passed in 0.07 seconds

[blueyed]

Thanks for the report!
This sounds like it might also cause the issues seen in pytest-django, which was handling Django's unittest by itself before pytest 4.2, and (had to) use pytest's mechanism in 4.2+ - causing issues there then.

[nicoddemus]

Hmm it seems this was introduced with the use of xunit fixtures for setup/teardown in unittest.TestCase subclasses.

item.parent.obj gives the class (not the instance), perhaps that's enough for your needs @westhomas? 🤔

[blueyed]

Yeah, related to pass_self=False in

pytest/src/_pytest/unittest.py

Line 70 in c92021f

cls, "setUpClass", "tearDownClass", scope="class", pass_self=False

.

[nicoddemus]

Yeah, related to pass_self=False

Are you sure or are you guessing? 🤔

They don't seem related because the example doesn't have either a setUp or setUpClass, and also if I comment out the code that injects the fixtures the behavior remains unchanged.

[nicoddemus]

Found the issue! Working on a fix. 😁

[nicoddemus]

PR open: #5393

[blueyed]

Are you sure or are you guessing? 

I've seen an error when changing it to True, which is the case with your PR still, and likely should just not be used like this then.. :D - i.e. I was guessing.. :)