SYSE.31:2 - Problem

A slow result arrives after the developer has changed context or several changes have accumulated. An unreliable result makes repetition cheaper than understanding. A fast but irrelevant result is equally dangerous: the suite can pass on one branch, one fixture or one old artifact while the integrated application fails.

The aim is not merely quicker execution. It is earlier useful discrimination between a usable change, an actual regression, a broken test or environment, and a question for which evidence is still absent.