Testing any non-trivial product is always a complex task and we do not claim to have all the bases covered. But midPoint is tested extensively, mostly using automated tests based on frameworks TestNG (with Spring testing extensions) and Selenide.
These automated tests cover many scenarios - and also documents them, although not necessarily on a level readable by analyst.
Check Unit Tests for most elemental tests and then check Integration Tests. Both types of tests use TestNG and all the tests extend from our subclasses providing basic facilities.
List of all testing topics: