@Test(expectedExceptions = ZusammenException.class)
public void testMergeNonExistingSource()  {

  Id itemId = new Id();
  Id versionId = new Id();
  mockExistingVersion(Space.PRIVATE, itemId, versionId);
  Id sourceVersionId = new Id();
  mockNonExistingVersion(Space.PRIVATE, itemId, sourceVersionId);
  itemVersionManagerImpl.merge(context, itemId, versionId, sourceVersionId);
}