Unit test data for each process defined in H.264 specifications?

I am currently writing a H.264 decoder in golang, and I'd really like to maintain testing for each unit of the entire package. What I'm struggling with is obtaining test input and output for the sub processes defined in the specifications.

I had a fair look over google, but can't find much. I have some ideas on how I can do this, one of them being to run a fuzzer over a good C implementation, but the C implementations I have found (good ones I guess would be ffmpeg and the reference implementation) hardly follow the specifications (likely because they're now highly optimised), so it's hard to distinguish 'boundaries' of the processes of interest.

Does anyone know of any test data lying around on the internet that would provide input and output for the processes defined in the specifications?