It's mostly a question of experience. I've been writing software long enough that when I give chat models some code and a problem, I can immediately tell if they understood it or if they got hooked on something unrelated. But junior devs will have a hell of a hard time, because the raw code quality that LLMs generate is usually top notch, even if the functionality is completely off.
> the raw code quality that LLMs generate is usually top notch, even if the functionality is completely off.
I'm not even sure what this is supposed to mean. It doesn't make syntax errors? Code that doesn't have the correct functionality is obviously not "top notch".
No syntax errors, good error handling and such. Just because it implemented the wrong function doesn't mean the function is bad.
High quality code is not just correct syntax. In fact if the syntax is wrong, it wouldn't be low quality, it simply wouldn't work. Even interns could spot that by running it. But in professional software development environments, you have many additional code requirements like readability, maintainability, overall stability or general good practice patterns. I've seen good engineers deliver high quality code that was still wrong because of some design oversight or misunderstanding - the exact same thing you see from current LLMs. Often you don't even know what is wrong with an approach until you see it cause a problem. But you should still deliver high quality code in the meantime if you want to be good at your job.