Reference models are fun, but for anything more than a simple web app, if you try to make them sufficiently different in implementation, you end up re-implement

Reference models are fun, but for anything more than a simple web app, if you try to make them sufficiently different in implementation, you end up re-implementing not only your business logic, but also a RDBMS functionality in your testsuite. Also verifying state of the app against the reference model after each testing step that modifies the state of the app also gets quickly out of hand. Even more so if you try to do it via public interfaces only. And there's no guarantee your model is right.