Putting voltage on the 2 slider shoes (for a about 2 sec or until the door starts to slide open) starts the operating cycle. To fully "test" the car you should confirm it automatically stops.
To do this, you must apply voltage to a center-rail roller and outer-rail wheel/truck. Th animation then continues, Santa will deliver a present, the door will reverse, and you should hear the gearmotor automatically stop when the door finally closes. The action stops even if you continue to apply voltage to the center roller and wheel. Start the next cycle by applying voltage to the 2 slider shoes.
I suppose one could argue that as long as the motion starts (via slider shoes) that the car "operates" and passes the test. But the stopping mechanism, which is a mechanical lever limit-switch is an integral part of the cycle operation, should be tested. There have been occasional OGR threads on this lever switch getting out of alignment, wire breaking off, etc.