If you’re not sure what a button does sometimes you’re better off just leaving it a mystery:
[…] At the time, mechanics were running the aircraft through a series of functional tests, according to Tim Wagner, a spokesman for the airline.
Amazingly, no workers were injured when the gear collapsed. During ground tests, mechanics often sit in the cockpit or stand near the belly of the plane.
I’m sure it’s a mistake any under-trained airline technician could make.