Abstract: Apparatus for testing the brake system of a motor vehicle has a housing which can be coupled to the rails for the driver's seat and supports a drive for a reciprocable depressing unit for the brake pedal. The depressing unit has a rear section which is movable by the drive and a front section which is movable with and relative to the rear section. When a cap at the front end of the front section engages and depresses the pedal, the cap is first moved against the opposition of a weak coil spring relative to a rear portion of the front section to thus close a switch in the circuit of two potentiometers, and the front section is thereupon moved relative to the rear section against the opposition of a helical compression coil spring. One of the potentiometers measures the distance which is covered by the rear section and the other potentiometer measures the distance which is covered by the front section relative to the rear section of the depressing unit.