TDD django models
If you don't want to drive yourself crazy, you should focus on tests that will really help you.  Testing that the id column is an integer isn't testing your code, it's testing Django.  Even testing that "subject" is a string field isn't helping you much.  Test that the models can do what they have to do.
If you're trying to do Test Driven Development, is it sane to write tests that check the column type of your models as you write your models?
Like before you write your model, you write a test and say I want an ID field that is an integer field.