Create test-only models within an app part of a larger project

I am looking for a way to create temporary models to test a simple django app part of a larger django project.

If it was not of the models I need to test the app, I would just create a "tests" directory within that app, however it does not work since it requires the migrations.

I'd like to avoid to:

• create a sibling test app with the tests in it
• create another application in another repository and install through pip
• pollute the database with the test models
• create the tables manually using SQL

I use both sqlite3 and MySQL. Django 1.9.5

What I tried:

1. Create tables manually
2. Django Fake Models does not seem to work