The browser.html team works on the frontend, so they are very much interested in improving this. You're right that Servo devs themselves often use an even more

The browser.html team works on the frontend, so they are very much interested in improving this. You're right that Servo devs themselves often use an even more stripped down test harness that you supply URLs to on the commandline, but that may change now that browser.html has gotten quite nice :)