Solved a Java 7 => Java 8 type-inference / generics incompatibility problem. The mock-argument-matching in this test is so obscure that really this test should be replaced with an IntegrationTest that just looks to the database to see if the expected changes happened.
The problems are caused mainly because it is pretty much non-deterministic which version of CrudRepository.save() gets invoked at runtime. Combined with importing static methods from two classes that are both called 'Matchers' (from both mockito and hamcrest), things get messy quick.

This may be related: https://bugs.openjdk.java.net/browse/JDK-8028442