TDD django models
I think it's a bit overkill to test the underlying framework within your app testing, in general.  Unless you have a suspicion that it isn't well-tested and/or it is something that may change a lot (say you live by developing against trunk), it should be a reasonable assumption that your framework will operate as advertised/documented.
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.