Originally Posted by AllanG

Sure you can test it, it is just a potentiometer. Using a voltmeter with the ignition on but engine not running, back probe the wiper wire at the connector. At idle you should see about 0.6v. Then slowly rotate the throttle quadrant and observe that the voltage increases steadily and smoothly with no flat spots. At WOT you should have a reading of around 4.8v if I remember correctly.

The wipers do wear over time and yes there could be ingress by oil or cleaning agents that could create a short but this test be an effective way verify the functionality of the TPS