id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
36083	LiveServerTestCase fails in parallel test runner if django.contrib.auth.backends has not yet been imported	Adam Zapletal	Adam Zapletal	"The full test suite run with multiple threads passes for me, but when I run the `tests.file_storage.tests` file in isolation (`./runtests.py file_storage.tests`), I get a failure. It passes in isolation if I run the tests with only one thread (`./runtests.py --parallel 1 file_storage.tests`). This happened to others when I asked about it in the Django Discord server, but not everyone. For what it's worth, I'm on the latest macOS running Python v3.12.

When a failure happens, I get the following error:

`django.core.exceptions.ImproperlyConfigured: AUTH_USER_MODEL refers to model 'auth.User' that has not been installed`

I have narrowed the issue down to the fact that this test file contains a class that inherits from `LiveServerTestCase`. It seems like any test file that mixes `LiveServerTestCase` and something more normal like `unittest.TestCase` will fail for me when run in isolation with more than one thread.

Here's a minimal example if anyone is interested:

{{{#!python
from unittest import TestCase

from django.test import LiveServerTestCase


class TestCaseTests(TestCase):
    def test(self):
        self.assertEqual(2, 2)


class LiveServerTestCaseTests(LiveServerTestCase):
    available_apps = []

    def test(self):
        self.assertEqual(2, 2)
}}}

I have a fix, but I'm not sure if it's a good one. Setting `available_apps = ['django.contrib.auth']` on the `LiveServerTestCase`-based class fixes it as one would expect from the error message, but I wonder if this is hiding something like a race condition. I wonder why it passes the full test suite when run with multiple threads, but it can't pass in isolation when run with multiple threads.

Should I open a pull request to fix [https://github.com/django/django/blob/8bee7fa45cd7bfe70b68784314e994e2d193fd70/tests/file_storage/tests.py#L1241 the test] in the way I mentioned above, or is something deeper going on here? It could be that I'm misunderstanding something about how `LiveServerTestCase` is isolated during test runs."	Bug	closed	Testing framework	dev	Normal	fixed	TransactionTestCase setupclass available_apps	Adam Zapletal Adam Johnson	Ready for checkin	1	0	0	0	0	0