Yes, so a bit of difference of opinion. I would err on the side of caution, as Harv says, it would be a right cock-up if I buggered up the handbrake on the way to the test !!!
I have a Lexus 300h and I hardly ever use the handbrake, although it is a footbrake like Mercedes, except for sometimes if I am waiting at long roadworks or slow traffic lights. The car doesn't object like the P38 when you pull it out of "P" on an incline so I just leave it in "P" whenever the car is left.