Additional Checks in UML-Java Transitive Change Tests

[HeikoKlare]

The UML-Java tests in the *.transitivechange.tests project currently only apply the linear network of PCM-UML and UML-Java transformations but do not validate the generated PCM models. In many cases, no PCM models are generated at all.
The tests still provide benefits, because they ensure that executing the UML-Java transformation bidirectionally and adding further transformations does not break anything. Nevertheless, in the cases in which a PCM model is created, it should be checked for correctness as well.

Thus, we should extend the UML-Java tests in the *.transitivechange.tests project to check the generated PCM model in cases in which such a model is generated.