You can buy a little outlet tester that includes a test for GFCI functionality for under 15 bucks. Anyone doing this kind of work at home should have one. And

You can buy a little outlet tester that includes a test for GFCI functionality for under 15 bucks. Anyone doing this kind of work at home should have one. And I get that it's more stuff to buy, but I've been learning that for all sorts of home repairs, even if I have to buy new tools to do it, and only use that tool once, I still come out cheaper than hiring someone to do it. Sometimes a lot cheaper.