That sounds like a sane test. If someone does blatantly cheat, it will be immediately obvious during the interview afterwards.

At my company, we ask people to submit some choice prior work if possible. Then we look at that, and try to have a conversation about the tech. The bonus is that it respects the candidates time, and it is easier to get them talking when it's their own projects. The downside is that very few candidates have recent prior work publicly available.