Investigate reducing the usage of Mockito #2534
Description
We have made good use of Mockito in the tests, however it doesn't play well with GraalVM native image compilation. As part of adding Graal support in #2533 we had to exclude 22 of these tests from the nativeTest execution.
We should investigate how much of this mocking can be replaced with standard classes, or simply using the actual components after the database has been set up in the way we expect for the tests