@Override
    protected void flush(MessageTuple item) {
        prepare(item);
        channel.flush();
    }
@Test
    public void testFlush() {
        Object message = new Object();
        NettyBatchWriteQueue.MessageTuple messageTuple = new NettyBatchWriteQueue.MessageTuple(message,
            mockChannelPromise);
        nettyBatchWriteQueue.flush(messageTuple);

        Mockito.verify(mockChannel).write(eq(message), eq(mockChannelPromise));
        Mockito.verify(mockChannel).flush();
    }