How to unit test netty handler

I implement a handler which extends SimpleChannelHandler, and overrides some methods such as channelConnected, messageReceived. However, I am wondering how to unit test it？

I searched about "netty unit test" and found one article which said considering CodecEmbedder, but I am still not sure how to begin. Do you have any example or advice on how to unit test Netty code?

Thanks a lot.