"Hey Mike, I'm sorry to have to report to you that my son broke your bindings on the board you loaned him. I bought you a replacement set, though".
Now, I'm happy that my friend replaced the broken bindings, but my first question back to him was "did you save the broken bindings?" He said yes, but I could tell by his voice that he was slightly confused. Wasn't I concerned that his son broke my bindings? Well, sure, but it wasn't a huge surprise. The board that I had loaned him was 15 years old, and was my "rock board". In good shape, but it had been through a lot. The bindings that were on it were likewise about 12 years old, and had been through lots of adventures with me over the years. Was it possible the bindings could break? Sure, it was possible. Still, I had seen or felt nothing to lead me to believe the bindings would fail prior to the trip. I made clear to my friend that I didn't blame him, or his son, for the break. Things happen. I was, however, very interested in trying to see what happened and why it happened, because the tester in me was fascinated. Based on what I know about the board, its vintage, the bindings, and the person who was riding it, I think I have a good theory on what happened.
My friend's son and I have wildly different skill levels. I've been riding for twenty years, and consider myself to be a very proficient rider. By contrast, my friend's son is closer to the novice level. He's still in the process of riding mostly on his heel edge, and not to the level where he can link heel-side and toe-side turns. This puts a lot more stress on parts of the bindings, especially the high-back attachments, for a much longer duration than I would put them through.
Also, my turns do not lean very much into the high-backs themselves. I touch a little bit, but most of my turning comes from my hips and legs, and the board follows along with my movement. In short, I transfer very little actual energy into the bindings themselves. They are there to hold me to the board, not actually wrench the board into place. My friends son, on the other hand, puts a lot of energy into the high-backs to hold himself up and keep himself stable. Additionally, that weight, because he favors heel-side, means that tension is constantly being held while he is actively riding.
The bindings were "high end" for their time, and in this case, high end doesn't really mean "super strong" or "bullet proof". In this case, high end means "high performance as relating to light weight". They were designed to keep the boarder in place if they landed with great torque for very short periods. They are really not designed for long term pressure on the high backs themselves. Different stressors brought out a weakness. In this case, the age of the bindings may have never been an issue for me, but for this other rider, the stresses led to a failure.
Analogous to software testing? Of course there is :). In this case, the parallel is that, as users, we each do things in unique ways, and those unique ways can shield us from issues that other people experience. A beginner puts totally different stresses on a system than a power user does. Some times, the stresses from the power user are the ones that can lead to problems, but occasionally, we find that a beginner may be the one to provide a stress we hadn't considered. It may be inexperience, it may be favoring a particular way of doing things, but if we don't consider both ranges of stressors, we may be optimizing one area while leaving another area vulnerable. This is where different personas can be vital. They make us reconsider who we are and what we are doing, and often, they let us see a world we personally would never consider.