> to ensure the code works correctly It's to ensure the code works correctly and indicate where the problem is, whenever it doesn't work correctly. Querying a

> to ensure the code works correctly It's to ensure the code works correctly and indicate where the problem is, whenever it doesn't work correctly. Querying a live database during unit tests fails on both accounts. It doesn't tell you whether or not the code works correctly - it tells you either that the code didn't work correctly or that the database wasn't available at the time the test ran.