Say what you want, followed by how you want it done, which includes unit testing, research (Claude can do research for you) on best practices, etc. I usually also follow up with "Why would I NOT want to do this this way, be critical of this." Usually outlines sensible issues, you give guidance, then the plan is ready to go. Then you test, test, and when you're done testing, you test some more, and review all code. I find that despite how busy that all sounds, I save myself weeks of effort.