There is a good chance there is a bunch of forms on the websites you work on. Login and signup forms, payment forms, contact forms, comment forms, etc. It's a good idea to test these forms. Certainly automated tests are a good idea. Backend tests that process the form data and test the results. Frontend tests that test the functions there are doing what you expect.
But then there is manual testing. Like, I want to test this with my eyeballs and my keyboard and mouse and emotions and stuff. That's probably the most common type of testing for designers. Certainly just filling out the forms by hand is a good idea, but doing that over and over gets so tedious you (gasp) might just not do it very often.
Perhaps we can just toss a little bit of code on our sites to prefill them when we need.