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.

Focus on endpoints that:

mutate important data

cross auth or tenant boundaries

involve multiple writes or transactions

depend on external systems

must handle retries or…