Write tests for the workspace switcher block

Why do we have to pass the requestStack and entityManager into the mock here? I don't think we need to inject dependencies into mock objects? Mock objects are just "fake", and we should be able to mock anything it needs to return, no?

There are a few more places where we inject dependencies into the mock. Please double check why we have to do this. I don't know much about PHPUnit, so maybe I'm wrong and just need some explanation ;-)