How Consumer Reports tests cars:

Braking

Good brakes are a vital component for safe driving. Our automotive engineers perform a series of brake tests from 60 mph to zero on wet and dry pavement to measure performance. The test car is rigged with a pavement-scanning optical device that records precise stopping times and distances. To evaluate antilock brakes, we use a wet roadway where the pavement under the left wheels is much slicker than the pavement under the right wheels. We also judge brake-pedal modulation.