The first thing any engineer (in any discipline) needs to learn when starting a real job is "the vendor is a lying bastard". I think it will work out substantially cheaper in the long run to test every strut rather than to go crazy with the material specification. Accept the universal truth that the vendor is a lying bastard, test as needed, and get on with life. If SpaceX ever reaches their reusability goal, the cost of all the testing will be spread across many flights anyway.
The second thing any engineer needs to learn is cost-benefit analysis:
1. I always choose the lowest bidding vendor, and he is always a lying bastard who can't deliver on spec, on time, or on budget.
2. Testing every part or losing rockets costs a lot of money than I saved on the lowest bidder.
3. Maybe I should vet my bids more carefully with plant visits, spot checks, and intermittent testing. Then choose the best vendor and not be cheapest one.
This approach will end up saving you money with high-visibility, low-volume projects.