Take a look at this section:

https://docs.djangoproject.com/en/5.2/topics/testing/tools/#django.test.SimpleTestCase.databases

There is a comment in there about overriding settings...

SimpleTestCase and its subclasses (e.g. TestCase, …) rely on setUpClass() and tearDownClass() to perform some class-wide initialization (e.g. overriding settings).