I agree, I also thought it wasn't clear if we were supposed to be writing tests, or code that was to be tested. Instead of modifying the test cases have them fill out a functions file and then run the random tests against those.
My fear with doing that is that if the functions file is separated from the tests file, then it becomes difficult to see at a glance what the function needs to do in order to make the test pass. That said, I agree that what you're supposed to do could be more clear -- would you care to open an issue so we can discuss it on the repo?