One really important test is a fatigue tests and heat test. A the fatigue test is essentially a device that will put a certain amount of cyclic loading to the device and will determine how many of those cycles it takes to fatigue. That number is documented and a safety factor is created. Another common test is a heat test which is supposed to simulate age. There’s a specific science which is able to understand and extrapolate the time it takes to reach failure based on a specific heat test.