@Override
    public final ChannelHandlerContext lastContext() {
        AbstractChannelHandlerContext last = tail.prev;
        if (last == head) {
            return null;
        }
        return last;
    }
@Test
    public void testLastContextEmptyPipeline() {
        ChannelPipeline pipeline = new LocalChannel().pipeline();
        assertNull(pipeline.lastContext());
    }