TestCase fixtures not found if inherited from other than first base class

[vilcans]

This is a regression from 1.6.5, where I inherited the fixtures attribute from a mixin class. In 1.7c1, Django acts like the attribute isn't there.

How to reproduce

from django.test import TestCase


class Mixin(object):
    fixtures = ('my_fixture',)


class Base(TestCase):
    pass


class FixtureTest(Base, Mixin):
    def test_dummy(self):
        pass

In 1.7c1, running this test gives no warning that the my_fixture doesn't exist, which shows that Django doesn't try to load it.

Workaround

Swapping the order of the base classes like this gives the expected result:

class FixtureTest(Mixin, Base):

Now running the test, Django tries to load the fixture, as it should:

/usr/local/lib/python2.7/dist-packages/django/core/management/commands/loaddata.py:225: UserWarning: No fixture named 'my_fixture' found.
  warnings.warn("No fixture named '%s' found." % fixture_name)

[vilcans]

Come to think of it, this may be good by design. Change the Mixin class to inherit from TestCase too and it works the way I expected it to. We get a diamond hierarchy but Python handles that well AFAIK.

[Claude Paroz]

This behavior change is caused by [abb10db06fb2ecb3e897462ec72417d10b39b8a4] (fixing #21089).

However when using mixins, the base class should always be the rightmost class. Read ​http://www.ianlewis.org/en/mixins-and-python for example. Therefore I'd tend to won't fix this ticket.

[Tim Graham]

I agree with Claude.