What you require - testing actual data changes - is not unit-testing and that's why you're not seeing it done in the tutorials. Unit testing tests business logic.
Here's a quote from the TDD Wikipedia entry:
The tests used for TDD should never cross process boundaries in a program, let alone network connections. Doing so introduces delays that make tests run slowly and discourage developers from running the whole suite. Introducing dependencies on external modules or data also turns unit tests into integration tests.
This is very good advise in my experience.
If you really want to test data changes you can set up another test project for integration tests. Keep the unit-testing clean and pure.