About Test bench in pictures.
I think it can not get absolute value testing, sure.
BUT,
with the some test machinery , in the some place and in the some situation, changing only motor.
You'll sure have one relative safe and precise comparative value.

So,
you can seed this is motor is better that that motor
( on that test motor stand, on that place , on on that temperature situation ).
That's not so bud![8D]