public ConcurrentHashMap<String, ConcurrentHashMap<Channel, ClientChannelInfo>> getGroupChannelTable() {
        return groupChannelTable;
    }
@Test
    public void testGetGroupChannelTable() throws Exception {
        producerManager.registerProducer(group, clientInfo);
        Map<Channel, ClientChannelInfo> oldMap = producerManager.getGroupChannelTable().get(group);
        
        producerManager.unregisterProducer(group, clientInfo);
        assertThat(oldMap.size()).isEqualTo(0);
    }