One time I sat down with a potential hire and went over a trivial PR. Nothing hard just some code to look at on GitHub to provide a familiar environment.

Why? To use it as a way to just look at our tech, get completely off track, and go down the tech rabbit hole. Good devs get really excited and talk about what they're using, what libraries they like, what they'd like to work with, etc.

Best hire I've ever made.