tx.begin();
_conn.invalidate(oid);
pg = (ProductGroupWithCollectionProxy) _conn.getObjectByIdentity(oid);
assertEquals("CollectionProxy size", 1, pg.getAllArticlesInGroup().size());
((InterfaceArticle) pg.getAllArticlesInGroup().get(0)).setArticleName("444");
tx.commit();
// test isolation of the cache
((InterfaceArticle) pg.getAllArticlesInGroup().get(0)).setArticleName("555");
tx = _kit.getTransaction(_conn);