Pragmatic Unit Testing in Java with JUnit, 3rd Edition

The Primary Benefit of TDD

With plain ol’ after-the-fact unit testing, the obvious, most significant benefit you gain is increased confidence that the code you wrote works as expected—at least to the coverage that your unit tests provide. With TDD, you gain that same benefit and many more.

Systems degrade primarily because we don’t strive often or hard enough to keep the code clean. We’re good at quickly adding code into our systems, but on the first pass, it’s more often not-so-great code than good code. We don’t spend a lot of effort cleaning up that initially costly code for many reasons. Joe chimes in with his list:

• “We need to move on to the next task. We don’t have time to gild the code.”

• “I think the code reads just fine the way it is. ...