What this catches
A healthy switch registers exactly one click per press. As the switch wears, the metal contact can bounce and send a second signal a few milliseconds later — that's chatter, and it makes files open twice, drags drop early, and shots double-fire.
Reading the result
Click the pad normally a few dozen times. Each press logs the gap since the last one; anything under your threshold flashes red and increments the fault counter. A few faults across many clicks can be coincidence — a steady stream of them means the switch is going.