Michael C. Feathers > Quotes > Quote > Corey Latislaw liked it

“Code without tests is bad code. It doesn't matter how well written it is; it doesn't matter how pretty or object-oriented or well-encapsulated it is. With tests, we can change the behavior of our code quickly and verifiably. Without them, we really don't know if our code is getting better or worse.”
― Michael Feathers, Working Effectively with Legacy Code