My Mouse Double Clicks On Its Own, How Do I Test All The Buttons Properly?

Two different things can cause what you describe, and one of them is not the mouse at all.

Windows has a folder option called Single-click to open an item. With it on, a single click opens folders, which looks exactly like a double click in File Explorer. Logitech's own support article lists it as the first thing to check. It will not cause double shots in games, though, so if you see both symptoms the mouse is the likely cause.

The mouse cause is the switch under the button. Each button sits on a small mechanical switch, and as its contacts wear or collect dust they can bounce, briefly making and breaking contact on one press. The computer sees two clicks.

The mouse test separates these. It counts each press per button, so you see the extra click directly, without File Explorer behaviour in the way. Test every button, including the side buttons and the wheel click, and note which one doubles. It is usually the left button, because it does the most work.

Then confirm it travels with the mouse. Run the same test on another computer. If the doubles follow the mouse, it is the switch. If the second computer is clean, look at drivers and software on the first. A short burst of compressed air into the gap around the button sometimes eases a dusty switch, but the lasting fixes are warranty, a switch replacement or a new mouse.