The review gate opens when the tests are green. Those tests were written by the same AI, in the same session, with the implementation in context — so they agree with the code instead of the requirement. Here’s how to tell, and what actually fixes it.
A lot of code is hard to test not because the business logic is complex, but because decisions and side effects are woven together. Functional Core, Imperative Shell is a simple rule for separating the two — and I pointed Claude Code at a tangled handler to do the split.
You have a service with zero tests. The backlog says ‘add tests’ but nobody picks it up. Here’s how Claude Code can get you to full coverage — and when to watch out.