[hef19898]

The first jet engines were used on actual aircraft during WW2, for obvious reasons speed trumped safety across the board. Heck, back then people thought installing liquid fuel rocket engines in wooden glider aircaft was such a good idea, they actually built and used them in combat. I'm too lazy to read up on the actual development history of the first jet powered fighter jets so.

And yes, depending on aircraft, a lot of components are tested until failure before they are installed in actually flying aircraft.