How to use pytest fixtures with Unittest methods

Question

class MyTestCase(unittest.Testcase):
    def setUp(self):
        self.something = True

    @pytest.fixture(autouse=True)
    def MyTestMethod(self, frozentime):
        fn(self.something)  # self.something is NOT defined

If I use @pytest.fixture(autouse=True) I end up with some strange behavior from PyTest. Instead of calling my setUp method before the test method, PyTest skips the setUp and calls MyTestMethod as if it was a PyTest MyTestFunction which of course does not work very well.

How do I get MyTestMethod to use the frozentime fixture without ignoring the setUp method that should be called first.

class MyTestCase(unittest.Testcase):
    def setUp(self):
        self.something = True

    #@pytest.fixture(autouse=True)
    def MyTestMethod(self, frozentime): # Fails on call, because it needs too many arguments.
        fn(self.something)  

Answer 1

That's because the autouse fixtures are executed before the setUp/tearDown methods:

Note

Due to architectural differences between the two frameworks, setup and teardown for unittest-based tests is performed during the call phase of testing instead of in pytest‘s standard setup and teardown stages. This can be important to understand in some situations, particularly when reasoning about errors. For example, if a unittest-based suite exhibits errors during setup, pytest will report no errors during its setup phase and will instead raise the error during call.

Source

There's nothing you can do to work around this behaviour. You can either move the fixture-relevant code out of setUp/tearDown methods, for example: if self.flag is used in class-scoped fixtures, you can replace

class Tests(unittest.TestCase):

    def setUp(self):
        self.flag = True

    def tearDown(self):
        self.flag = False

    @pytest.fixture(autouse=True)
    def myfixture(self):
        print(self.flag)

with

class Tests(unittest.TestCase):

    @pytest.fixture(autouse=True)
    def prepare_flag(self):
        self.flag = True
        yield
        self.flag = False

    @pytest.fixture(autouse=True)
    def myfixture(self, prepare_flag):
        print(self.flag)

Or you can move all the setUp relevant code from fixtures:

class Tests(unittest.TestCase):

    def setUp(self):
        self.flag = True

    @pytest.fixture(autouse=True)
    def myfixture(self, somearg):
        fn(self.flag, somearg)

becomes

class Tests(unittest.TestCase):

    def setUp(self):
        self.flag = True
        fn(self.flag, self._somearg)

    @pytest.fixture(autouse=True)
    def assign_stuff(self, somearg):
        self._somearg = somearg