I just really use an old fashion 8 port KVM setup and keep a couple newer computers handy if I need to test some memory or daughter cards. I also have a dell precision T3500 with a hot swap hard drive slider in one of the front bays to do testing and wiping of SATA drives. If I have a need to test monitors, I just hook them up to my laptop, have one that has a vga and hdmi outlet. Any thing else that I can't test, I probably don't need to test, so it goes to scrap.
I have seen bigger, more custom set-ups for when you need speed in your testing, but for a little guy in the e-waste
world, I pretty much have it all covered with this. Nothing too fancy at all. Hope this helps you a little.