[samatman]

Good question actually.

There are a few options. I work with a REPL, so I usually load the answer from a scratch file and put some representative data into it. When the result is wrong, which often happens, I feed ChatGPT the error, and it corrects the code accordingly. Iterating this results in a working function about 80% of the time. Sometimes it loses the plot and I either give up or start over with more detailed instructions.

You can also ask it to write tests, some of which will pass, some of which will fail. It's pretty easy to eyeball whether or not a test is valid, and they won't always be valid, I just fix those by hand.