It Just Works Perfectly

Your code passes all the tests and deploys without errors. Everything's green. Ship it. Then you take one look at the actual implementation and realize the entire thing is held together by a chain of else if statements, each one more structurally unsound than the last. Sure, it technically functions. So does a building propped up by wooden poles after an earthquake. The real question isn't "does it work?" but rather "how long until someone needs to add a feature and the whole thing collapses?" Spoiler: it's tomorrow. And that someone is you.