My mock server lied to me. So I built a stateful...

Last month I was integrating with a payment API. Wrote my tests against a mock server, everything passed, shipped to staging — and the whole flow broke. The mock told me POST /charges returns {"id": "ch_123"}. And it does. But my code then called GET /charges/ch_123 to verify the status, and the mock returned 404. Because the mock doesn't actually store anything. Every request lives in its own universe. I lost half a day to this. And it wasn't the first time. The problem with stateless mocks I'v