http://blog.8thlight.com/uncle-bob/2014/05/19/First.html
blog-post-first#confidence-leads-to-speed1 Confidence. A well designed test suite with a high degree of coverage eliminates, or at least strongly mitigates the fear of change. And when you aren't afraid to change your code, you will clean it. And if you clean it, it won't rot. And if it doesn't rot, then the software team can go fast. blog-post-first#confidence-leads-to-speed1