I worked on many Aircraft and the rules are extremely Stiff, even down to using a washer out of a new packet IE if you needed 101 washers and you have a pack of 100 the batch and part number has to be entered on to the Data Sheet along with the Date they arrived in to the stores and including the Date they were tested and by Whom, and like food they all have a shelf life and then they are Dumped. and when you open the New packet to take out the one extra you need you have to enter the same Date in to the Data Sheet of the Item you are Building, There is No Grey Areas when it come to building Planes, If you use a part/washer without entering the Data or use a washer that is not on the list you will be Fired quick Smart,
As for Testing things like Bulk Heads and Doors etc we built in House testing Jigs that cost over Half a Million Dollars in order to do a 30 second test and then they were Scrapped, Which I didn't mind because I got many hundreds of meters of Aircraft Quality Steel Cables out of the Skip to use as Tow Ropes, LOL,
Bottom line is Plane Safety at the Factory is Insanely High, even more excessive than a Visiting US President or Royalty. :Y: