Created on behalf of the following GitHub issue:
https://github.com/camunda/camunda-bpm-assert/issues/66

Currently we print out error messages like:

java.lang.AssertionError: Expecting actual ProcessInstance {id='4', processDefinitionId='process_skipTaskAndEvent:1:3', businessKey='null'}
to be ended, but it is not!. (Please make sure you have set the history service
of the engine to at least 'activity' or a higher level before making use of this assertion!)

We could check the used level before making such a suggestion in order to not lead the user in the wrong way.