“Years ago while interning in the rendering group at Pixar, I learned an important lesson: “interesting” things almost always come to light when a software system is given input with significantly different characteristics than it’s seen before. Even for well-written and mature software systems, new types of input almost always expose heretofore unknown shortcomings in the existing implementation.”
—Matt Pharr. Swallowing the Elephant (Part 1) pharr.org. July 8, 2018.
Probably true of any system.