You can use the application to test out each key on your device. When you press a key, it will be illuminated in green on the corresponding image of the keyboard on your screen. There are different models and different colors available. Untested keys are shown in yellow.
KeyboardTest will also give you interesting information about pressing your keys: the value of the pressed key for Windows and for BIOS, keystrokes per second, any delay between key presses, and more.
Another interesting detail included in the application is the ability to establish personalized keyboard layouts, and run batch tests through the command line.