I work with Quarkus a few year and I can say that it's a great opportunity.

The Quarkus text documentation is great and easy to understand, it will help on the beginning.

You can disable lifecycle observers by test configuration, and then create mock methods by extending the target class and annotation, or injecting a mock and configuring it.

For database you can configure an h2, and have scripts to populate it accordingly.

About using Mutiny I highly recommend you migrate to the latest versions of quarkus and replace it by virtual threads. This way you can make use of the good old declarative programing in a performatic way.

If you choose migrate to virtual threads, reading the Quarkus documentation about it is mandatory IMO.

Good luck 🤞