As we keep adding more interactions we want to cover, and keep adding new kinds of tests, adding a test file per interaction per kind of test is becoming painful, and we tend to miss things that would be nice to cover, but not the most important at the moment. I would like to change the way the tests in https://searchfox.org/mozilla-central/source/browser/base/content/test/performance/ are organized, so that all the testing code lives in head.js and so that individual test files only cover triggering a user interaction and providing whitelists. This would make all the kinds of performance tests we have (reflow, js modules/components loaded, flickering, image loaded but never painted, <future types introduced later>) opt out.