Test Driven Development

There is a lot to be written about test driven development, or TDD for short. If there is however a single thing to remember I would argue that is the following:

“Red, green, refactor”: Write a failing test, make the test pass, then refactor.

Ofcourse one can go on about the limits of TDD, and where it falls apart. Building a new software system using TDD mechanics is the easy part. Refactoring an existing system using these same practices is the hard part. In fact it is quite possible that some areas of an application cannot easily be tested, or at least not in a way where the effort required to properly test a system outweighs the discomfort from a broken system.