Testing strategy for custom Quarkus extension

[steinsag]

Based on Quarkus REST Client, I implemented an API adapter for a complex API including caching, retry strategy, paging, etc. Now, I want to re-use this API adapter in another Quarkus microservice, which also needs to talk to this API. Therefore, I thought about moving the API adapter into a custom Quarkus extension.

I have full test coverage for the API adapter by spinning up Wiremock to simulate the external API with different scenarios. Of course I would like to move testing also to the extension project so that I can develop the API adapter in a test-driven way.

I struggle to understand how to do testing of extension code. My extension does nothing as long as nobody is injecting my exposed bean. So it seems the usual deployment-module QuarkusUnitTest approach is not what I'm looking for.

I looked for examples and found https://github.com/quarkiverse/quarkus-google-cloud-services/tree/main/firestore

There, they also have no single "unit" test. Instead, they rely on integration tests where they write a small application using this extension. Is this the right approach or am I missing something?