If you want to contribute unit tests, I believe that Linus would be open to the idea. For example, there are a bunch of internal APIs: linked lists come to mind. If you wrote unit tests for an internal API, he might accept it. I would start very small -- one .c file with no more than 20 unit tests -- to gauge if there is interest from the community. It seems like a nice gateway to get junior developers (university-level students) in the kernel development. Reading open source mailing lists, I have learned that the best way to "break-in" is a tiny code change that is well-tested. It is hard to reject this type of submission. Be unopinionated, but competant in your submission, and they will be open-minded.