From an Engineering point of view. If the eng run is carried out by the flight crew with all cabin crew present then as long as local and company procedures are followed it is ok with pax on board.
My present employer insists that if engineering staff are carrying out the run then all pax and crew are off, doors closed, bridges off etc. Minimum of two Licensed Engineers on the flight deck and numerous Mechs/techs outside. Tricky at a line station...
