API integration tests aren’t about checking 200 OK . They exist to answer a harder question: When a real request crosses authentication, validation, persistence, and transactions — does the system behave correctly? Most production bugs don’t live inside a single function. They happen between boundaries . What Integration Tests Should Actually Prove A useful API integration test verifies: routing + request parsing authentication & authorization validation and error shape database writes and reads transaction boundaries response contract retry / duplicate handling concurrency behavior This sits between unit tests and end-to-end tests: Unit → logic correctness Integration → system behavior at boundaries E2E → full user journey Start With Risk, Not Coverage Don’t write the same number of tests per endpoint.…