I've written some ROMs for Williams System 3, 4, 6 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.
System 6 games:
System 4 games:
System 3 games:
They are 2716 (2K) ROMs and can also be used in a 2816 EEPROM.
You can get them all in a single zip file here: http://pincoder.reversion.ca
Hope this helps!