one way to test whether the ABS is working is the following:
* jack up the rears and place them on jackstands. Make sure they are VERY stable. Make sure the fronts are properly secured so that they do not move.
* start your car and run it through the gears until it reaches a certain speed on the speedo.
* apply the brakes. Since the fronts are not rotating, the ABS will be activated (i.e., the system will be fooled), and you will feel the pedal pulsing. I believe it will be pulsing for the fronts, because the system thinks the fronts are skidding.
Again, make sure that the car is jacked very securely before attempting this.