Hi,
I've written some ROMs for Williams System 3-7 pinball machines games that are very simple to use, and can be used in-game, so you don't need any test fixtures.
Install and power up each ROM in order to quickly help you identify problems with your entire machine.
You can get them all in a single zip file here: http://pincoder.ca
There is also a thread on this site where you can leave some feedback: https://pinside.com/pinball/forum/topic/new-williams-system-6-in-game-test-roms