It is amazing for typing out mock data. Say you're testing parsing of XML - it can easily suggest the the assertions over the data parsed from the XML. Example test that was 95% coming out of Copilot: https://github.com/dotnet/arcade-services/blob/61babf31dc63c...

It also predicts comments and logging messages amazingly well (you type "logger." add 7/10 times get what you want, sometimes even better), incorporating variables from the context around. This speeds up the tedious parts of programming when you are finalizing the code (adding docs + tracing).

Honestly, Copilot saves me so much time every week while turning chores into a really fun time.

I wrote up some notes on a recent experience I had writing tests with Copilot here: https://til.simonwillison.net/gpt3/writing-test-with-copilot

Once you get the hang of how to prompt it (mainly through clever use of comments) it can be a HUGE time saver.

Yes, if you show an example, or even have the test file open, it will make the other tests for you.

The best part about it for me is just the Intellisense (in Typescript). I'm using it on probably 3/5 lines that I write as a smarter version, but I rarely use it to do more than finish the current line I am writing.