I found a few items from my checklist w/o too much effort. I know I did a longer one here years ago but am not sure how to find it.
Here's some things to check when you find one:
1) Play some games. Games should play well w/o any glitches.
2) Do game high scores save correctly? Look for them being non-default when the game is powered on.
Go to diagnostics mode and check out all of the options.
a) Listen for game music (cheap squeak board) and game sounds (SSIO board) in the sound diagnostics menu. This also exercises the dual amp board -- make sure that EVERY game sound comes out in the tests because if some are silent you have a bad dual amp board or SSIO problem.
b) Go to the user input screen and press every button and trigger and steering wheel move and gas pedal movement. Every button/trigger should make a sound (SSIO board) and light a light on the game (lamp driver board). You should get a nice smooth progression of values on the gas pedal and steering wheel when you turn/move them. Gas pedal should return a value of 0 to about 20 hex when it is pressed. Most have original bad pots and max value is only about 1c or 1e -- bad news because you don't get turbo in the game like you're supposed to. Make sure you press the weapons van button to make sure that the light comes on. Exercise every control!!!
Sideart is usually faded or bad if still original.
There are additional things to look for if you have a linear power board.
I'd recommend opening the control panel and looking at the springs used for tension and how they are wearing on the metal board they hook into. Eventually they will break or tear their way through the metal board.