Django: Adding a test that has its own set of models

I have a peculiar Django package that defines tools for working with models. This means that I need to write tests in which I define a bunch of model classes, and then do tests on them. Note that for each test, I need to manually write a separate collection of model classes.

Is that possible with Django? How can I tell Django "for this test, please use these 7 model classes I defined"?