Testing using multiple languages

[Charles Law]

I have a python 3 version of protobufs that I want to test.  It passes all the unittests, so I know it can decode what it encodes, but I want to test it that it can talk to clients written in other languages.  I noticed when I was making the python 3 version, I had some mistakes in the encoder that were hidden because of mistakes in the decoder.  I think I got rid of them all, but I would like to talk to other types of clients to really be sure.  Has anyone done testing like this before?  Are there any good ways to test this?