Reddit mentions of Thx lucasfilm

Pioneer produced a disc of test material specifically for their players. You can still find a [listing for it] (http://parts.pioneerelectronics.com/part.asp?productNum=GGV1069) on Pioneer's site, but they no longer sell it. Finding one is next to impossible, but they pop up on EBay and on LD forums every once in awhile.

The defacto "go to" test disc by and large is the LD version of [Joe Kane's Video Essentials] (http://videoessentials.com/products/video-essentials-laser-disc.html). Again, no longer sold new, but they're a lot easier to come by than the Pioneer factory disc.

There's the [THX WOW! disc] (http://www.lddb.com/laserdisc/19090/THX-WOW/THX-WOW!-(1990)), 2 of which are currently listed for sale on [Amazon] (http://www.amazon.com/THX-Lucasfilm-Demo-Laserdisc/dp/B00BCNJT0Q)

Also the [Hitachi Destination Groovin disc] (http://www.lddb.com/laserdisc/53336/DN-GV-94001/Hitachi-Destination-Groovin). Hard to find but there's an unsleeved one [on Ebay right now] (http://www.ebay.com/itm/Hitachi-Destination-Groovin-DN-GV-94001-Test-Demo-Disc-NOT-ON-DVD-HTF-LD-/141442558254?pt=US_Laserdisc&hash=item20eea2292e) for $49.95

And the Japanese [Tune-Up A.V. disc] (http://www.lddb.com/laserdisc/28184/50LS-5023/Tune-Up-AoeVoe-(1988)), which you can find good copies of on Ebay for around $20-30 pretty frequnetly.

There were discs produced just to demonstrate Dolby and DTS sound, but the above mentioned titles will be more useful. I'd start with Video Essentials, if you can find a copy (ebay) and pick up the others if and when you want to try them out.

As far as "known good" discs, that's tough. Certain batches of certain titles are known to have a lot of rot problems, but otherwise it's just down to how the disc was kept and whether or not that individual disc happened to be improperly pressed in a way that would lead to rot.