As a helicopter mechanic, licenced and rated on several types in Australia, Fiji, and PNG, I would not ground run a machine unless I had a pilot at the controls.
Having said that I know of a Bell47 doing pirouettes on wet grass when the bricks fell off the pedals when someone ???? was doing a fan balance at 2 am dark o'clock, dragging oneself along the basket to get to the throttle took some doing.
Years ago at Army Aviation Base Oakey, SNCOs were approved to do ground runs on 3B1s.
To pull enough power to get the turbo to bootstrap six diggers were stood on each skid and collective was pulled.
During one particular ground run one person fell off the left skid, the machine rolled over resulting in death and destruction.
Needless to say this practice was banned.
My personal risk mitigation is that unless you can fly the machine, don't run it.
FWIW