A
proof test is a form of
stress test to demonstrate the fitness of a load-bearing structure, or rescue strop. An individual proof test may apply only to the unit tested, or to its design in general for mass-produced items. Such a structure is often subjected to loads above that expected in actual use, demonstrating
safety and
design margin. Proof testing is nominally a
nondestructive test, particularly if both design margins and test levels are well-chosen. However, unit failures are by definition considered to have been destroyed for their originally-intended use and load levels.