Open an online mouse test and click each button to verify it registers: left, right, middle (scroll wheel click), and side buttons (back/forward). The test should show which button was pressed and log each event. To test for double-click issues (where one click registers as two), click the left button slowly and check the event log — if you see two events per click, you have a switch debounce problem. Test scroll wheel direction and smoothness by scrolling up and down. Drag testing: hold left click and move the mouse — if the click releases unexpectedly during a drag, the switch may be worn. Test at different click speeds to detect intermittent failures. This works with all mouse types: wired, wireless, Bluetooth, and trackpads.