The sticker etc is testable and the k factor has to match, but the manual states a reason for failure is "operating at an incorrect speed"


Not working at all isn't a fail at a testing station, as said we were told to just assume our machine didn't work. We used to pop the seal and plug into it with a handheld tester, and can simulate speed, the throttle will kick when the governed speed is reached. If that speed was wrong it was a fail, if it didn't stop at all, its a pass


TBH its far easier on the new tachos, to test them, but most of the older ones never worked at all. But then you get drivers arriving with no cards in them


Road side would have you by looking at tacho data etc though