Good questions, Ralf.
Support for counterexamples, including automatic generation of test cases, is something that we've planned for years, but unfortunately we still haven't got around to implementing it. Hopefully we will do that in that not too distant future.
Although you can't display fact tables on the diagram page like in the ORM book, you can achieve something similar by dragging a sample population editor window near the fact type shape. You can also open multiple copies of a sample population window at once.