In java this kara was fun up until the output stream requirements. I don't know if it's better in other languages but the output stream bits didn't seem clear to me from the instructions.

As well as it being unclear I also really dislike the output stream test with duplicate label, it seems off to me that you want both the requirement to have jump forwards forcing marks to be pre-processed but then you expect the exception to be thrown inline during program runtime if a mark is duplicate. While not difficult to code to these requirements it just doesn't feel like a nice solution.

I've improved the java tests including the addition of random tests if anyone wants to approve it: https://www.codewars.com/kumite/638f44ccbb8c010058658dc8?sel=638f44ccbb8c010058658dc8

Brainfuck translation if anyone is interested: https://www.codewars.com/kumite/638e1fe259b85d004a0f133f?sel=638e1fe259b85d004a0f133f