I like reading about software history and this is a new angle to approach it from. When did people start testing one another on this particular thing, and why n

I like reading about software history and this is a new angle to approach it from. When did people start testing one another on this particular thing, and why not this other thing? I learned how to write linked lists in some first year comp sci course in the mid-90s and used them extensively in my first job after graduating, which was writing database software in C. I'm sure I was asked about them in various interviews afterwards, most of which involved no C whatsoever, and I'm equally sure I thought this was a completely normal thing to ask. In retrospect, it does seem strange.