Ken, #332; it depends on who ‘they’ are.
ICAO, the State(s) of manufacturer / operation / location; regulator, civil / military, manufacturer(s), airframe, engine, FADEC, software, validation, …
There’s probably a link to NTSB in there somewhere: who’s ball, who’s playing field.
What requirements apply to fight test - see all of the above.
Off thread, who investigated the Nov 9, 2010, Boeing 787, ZA002 battery fire ?