I think it's worthwhile! Lack of a comprehensive test suite means: 1) There are seem to still be regressions in pretty fundamental stuff when new features are

I think it's worthwhile! Lack of a comprehensive test suite means: 1) There are seem to still be regressions in pretty fundamental stuff when new features are added. Usually caught before things reach "release" trains, but I see it in bug trackers all the time. 2) Other layout engine managers I've talked with who want to do a layout system rewrite are terrified of anything that doesn't look like a large-scale refactoring because of this issue. I've had the "how are you testing and measuring progress / how do you know you're done with layout?" conversation with most of our engine peers at this point :-)