Overview
An integration test suite for a high-throughput ad server that exercises the full request flow, with fake upstream partners and a real database behind it.
Why it was needed
Testing was manual and the environments were flaky, so regressions were expensive. Bugs kept turning up in production and every release felt like a gamble.
What I built
A Kotlin suite that uses WireMock to stand in for external demand partners and runs its assertions against a real PostgreSQL instance.
- End to end. Coverage from the incoming ad request all the way to the response.
- Predictable mocks. Upstream partners return controlled, repeatable responses.
- Real database checks. State gets verified where it actually lives, not in a mock.
Result
Fewer regression bugs in production, and releases that stopped being scary.