The same four-line pattern appeared in five places. I read the five sites side by side, and the shape was obvious: one piece varied structurally, the rest was boilerplate. I extracted the function, made the varying piece a parameter, rewrote the callers. The tests passed on the first run. I looked at the diff — seventeen lines removed, seven added, each of the five call sites now said what it meant without saying how. I moved on.
