Write Integration Tests

When writing integration tests:

1. Identify the integration boundary: database, external API, file system, message queue.
2. Use a real instance of the dependency (test database, test server) — avoid mocking the boundary.
3. Set up test data in a before/beforeEach block. Clean up in after/afterEach.
4. Test the full path: request in, processing, storage, response out.
5. Test failure modes: connection timeouts, invalid responses, missing records.
6. Keep integration tests isolated — each test should create and clean up its own data.
7. Tag integration tests so they can be run separately from fast unit tests.