A method and apparatus are disclosed for using a general purpose input-output (GPIO) interface to test a user input device such as a wireless keyboard or mouse. Operation of key-scan logic can be tested by the GPIO interface by temporarily disconnecting the outputs of the various rows and columns and substituting signals generated by a test algorithm into the input terminals of the key-scan logic. The test signal is processed by the key scan circuitry and a key-scan output signal is generated. This key-scan output signal is then compared to a known reference output signal to determine if the key-scan logic and associated circuitry is operating properly. Other embodiments of the GPIO testing system can be used to test other user devices such as a computer mouse/scrolling device.