@Override
    public final ChannelHandlerContext firstContext() {
        AbstractChannelHandlerContext first = head.next;
        if (first == tail) {
            return null;
        }
        return head.next;
    }
@Test
    public void testFirstContextEmptyPipeline() {
        ChannelPipeline pipeline = new LocalChannel().pipeline();
        assertNull(pipeline.firstContext());
    }