I recently visited the Japanese factory where Denon and Marantz make the hi-fi and home theater gear, and the best part of the seeing the facility was getting a demo of the reference home theater listening there, with its 9.4.6 channels of Dolby Atmos sound delivered via $250k of Bowers & Wilkins speaker.
While snooping around the room, the shelving in the corner that houses their disc library naturally caught my eye. Marantz's engineers had already told me that they consider Gravity to be one of the ultimate stress tests for AVRs (you can read why in the piece I linked above), but what else do they keep on hand for testing AV receivers and other gear?