How does Boeing test the braking limits on the largest aircraft they’ve ever built? File the brake pads down to the rivets, load up the plane to nearly a million pounds, gun the engines to beyond takeoff speed (~200 mph), then mash the brakes as hard as possible and watch them burst into flames. As long as damage is contained to the brakes and wheels, the test is passed. Bonus: The 747-8F stopped 700 feet sooner than expected.
(Video courtesy of Boeing)