Testing

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.