Smoke: Black-Box Route Testing the Router Gates Itself
Every unit test was green. The page returned 502 anyway.
The route was a treasure generator. Its store had a thorough test suite, all passing, because the test built the store the way the test knew to build it – with the database pool wired in. Production built it differently: a copy-paste in the route setup left the pool out, the store carried a nil handle, and the first query dereferenced nil. The handler panicked, the connection dropped, the reverse proxy turned that into a 502. No test caught it, because no test exercised the wired route against a running server. The tests checked the parts. Nothing checked that the assembled thing served.