int deliveringCount = queue.getDeliveringCount();
assertEquals(1, deliveringCount);
List acknowledging = r.getMessages();
assertEquals(1, acknowledging.size());
Message ackm = (Message)acknowledging.get(0);
assertEquals(0, ackm.getMessageID());
// non-transacted acknowledgment
r.acknowledge(ackm, null);
assertTrue(queue.browse().isEmpty());