I've shipped CitizenApp with nine AI features in production, and I can tell you with absolute certainty: bad tests in FastAPI will destroy your confidence faster than any outage. I'm not talking about unit tests that mock everything into oblivion—those are security theater. I'm talking about real tests that hit PostgreSQL, verify transactional behavior, and catch the subtle data corruption bugs that only appear under load.
Here's what actually works, and why most FastAPI test guides miss the point entirely.
Why Your Current Tests Probably Suck
Most tutorials show you how to mock the database. That's fine for toy projects. In production, I've watched carefully mocked unit tests pass while the actual endpoint corrupted customer data because of transaction isolation issues, cascading deletes, or constraint violations that only emerge with real schema interactions.
The problem: when you mock everything, you're testing your assumptions, not your code. Your assumptions are usually wrong.
