Hmm. It’s more like you want to hear the musician play first, but you don’t ask him to play something he is comfortable with to learn how skilled he is, nor do you ask him to play a known challenging piece of work. Instead you just start pulling out short “gotcha” songs with obscure key shifts and speed changes to test them. Like, sure a great musician will be able to handle it if they are a great musician, but it’s just annoying for the musician and there should be better ways to determine if they meet your expectations.