((ImplementationImpl) odmg).setOqlCollectionClass(DListImpl.class);
//=============================
tx.begin();
OQLQuery query = odmg.newOQLQuery();
query.create("select x from " + Article.class.getName() + " where productGroupId = 7");
List results = (List) query.execute();
int originalSize = results.size();
assertTrue("result count have to be > 0", originalSize > 0);