A proof test is a test wherein a eliberately overpressured round is fired from a firearm in order to verify that the firearm is not defective and will not explode on firing. The firearm is inspected after the test, and if it is found to be in sound condition, then it is marked with a Proof Mark to indicate that is has been proofed (not proven). In many jurisdictions a proof test and valid proof mark are required for the sale of firearms.