One of the coolest (& scariest) tests they perform is a tensile strength test, sometimes called tension testing. Basically what they do is put stress on a rod (in this case they bend it) in a controlled manner. They keep adding stress to the rod until it breaks. As they go along, they keep measuring both the flex of the rod - how much it bends, & the stress, or pull, on the blank. When the tests are all done, they know exactly how much the rod should bend with a certain amount of weight pulling on it. ("With the rod pulling 4 lbs, it will flex this much & will act this way.....").
Normally this isn't just a test to see if their designs came out correctly. Sometime it is, but they learn a lot from these tests & use what they learn in future rod designs & tapers. By keeping track of everything, like how much & the specific type of graphite fibers used in certain spots of the rod, they can see exactly how it will work in a finished rod. They then use this information to design rods for specific types of fishing.
They used to run these tests on rods back in the bamboo days, too. Though if they ever tested one of my bamboo blanks like this until it broke, I'd have to be out of the room I think. After all my hand splitting, sanding, & planing I don't think I could stand to watch it.
So here's a very short video of the Hardy company doing one of these tests to a rod at their facility in England. I must warn you that if you're jumpy, put the coffee down right now. The end will catch you by surprise. Also, notice where the rod breaks in the video - about one third of the way up from the contraption that's holding it & not at the tip where you might think that it would. Very interesting.