I think, from your posts / expertise you are 'in the trade' and may even do MOTs.
I'm curious, how do the test the 'handbrake' on cars with electronic, push button ones. Also, what about cars (like the Outlander PHEV) which don't even have that- just a P button and a 'Hold' button (this stops 'creep', when you select it the car won't creep forward etc after you've stopped at, say, traffic lights, unless you touch the acc. (No need to keep your foot on the brake like in an Auto.)
As I say, I'm just curious- my PHEV isn't due an MOT for sometime.
(I'm also curious re the way the 'drive system' will respond on the 'rollers' and how they will ensure the engine is 'warmed up' for the emission tests - they must have a method as some PHEVs must be old enough for MOTs. The emissions are very low, as I recall, around 40g/km, so perhaps there is a special method.)