Then your choice is whether you want to hire people who only know C++. For some jobs, you don't. But if you do, you need to have multiple tests and choose one b

Then your choice is whether you want to hire people who only know C++. For some jobs, you don't. But if you do, you need to have multiple tests and choose one based on the candidate's skills. We have an in office test--the dev sits down at a laptop with internet access, gets clear instructions and scaffolding code. We know that the tasks take n minutes because we see the time that candidates take.