Speed and health in one test
The right button gets far fewer presses than the left, so faults often go unnoticed. Clicking quickly here surfaces two things at once: how fast you can right-click, and whether every press is actually registering.
If the count looks wrong
A right button that skips presses or counts extras is usually a switch issue. Pair this with the double-click test to rule out chatter on the right button specifically.