Grails 2.0.0 Update: Test Problems

Grails 2 has some nice improvements over the previous 1.3.x versions and we thought we give it a try. Upgrading our application and its 18 plugins went smooth (we already used the database migration plugin). The application started and ran without problems. The better console output and stacktraces are a welcomed improvement. So all in all a pleasant surprise!
So just running the tests for verification and we can commit to our upgrade branch. Boom!

junit.framework.AssertionFailedError:
No more calls to 'method' expected at this point. End of demands.

Looking at the failing unit test showed that we did not use any mock object for this method call. Running the test alone let it pass. Hhhmm seems like we hit GRAILS-8530. The problem even exists between unit and integration tests. So when you mock something in your unit test it is also mocked in the integration tests which are run after the unit tests.
Even mocking via Expando metaclass and the map notation did not work reliably. So upgrading for us is not viable at the moment.