A lot of things that we use all the time couldn't be reasonably tested in operational scenario in any other way than by just using them(most planes are in that category - you can test a lot of things on test benches but there isn't a way to test an airliner at operational speed an altitude other than actually flying it)
I think if SpaceX can send 15 robotic rockets into space to test them, this lot could've sunk a prototype to high pressure and got a diver to go down and smack the hull with a wrench for a while.