I don't know how you gonna test them, but if you switch on the ignition keys and start the engine, some vacuum will be created in the system and then press the rear headrest switch, making sure that you have raised both of them to upright position and see if they both fall together almost. If so, then your vacuum system should be ok. How ok it is I won't know because this vacuum circuit controls a lot of other things in the car, maybe even the doors and the aircon system and the air-circulation system in the car. Try to listen for the whirring sound coming from somewhere in the rear boot next to the fuel inlet, under it. This is the vacuum pump location. If its noisy, its going out soon. Sure to be leaking somewhere. There can also be another whirring or buzzing sound, but that is the fuel pump under the car near the right wheel(or left). If thats making noise, then thats also going too. I'm no expert, but hear this from many people with the same problems. Good luck.