One thing I do is go to Leetcode, see the optimal big O time and space solutions, then give the LLM the Leetcode medium/hard problem, and limit it to the optimal big O time/space solution and suggest the method (bidirectional BFS). I ask for the solution in some fairly mainstream modern language (although not Javascript, Java or Python). I also say to do it as compact as possible. Sometimes I reiterate that.

It's just a function usually, but it does not always compile. I'd set this as a low bar for programming. We haven't even gotten into classes, architecture, badly-defined specifications and so on.

LLMs are useful for programming, but I'd want them to clear this low hurdle first.