Test-driven development

Let's talk briefly about test-driven development (TDD). It is a methodology that was rediscovered by Kent Beck, who wrote Test-Driven Development by Example, Addison Wesley, 2002, which I encourage you to check out if you want to learn about the fundamentals of this subject.

TDD is a software development methodology that is based on the continuous repetition of a very short development cycle.

First, the developer writes a test, and makes it run. The test is supposed to check a feature that is not yet part of the code. Maybe it is a new feature to be added, or something to be removed or amended. Running the test will make it fail and, because of this, this phase is called Red.

When the test has failed, the developer writes the minimal amount of code to make it pass. When running the test succeeds, we have the so-called Green phase. In this phase, it is okay to write code that cheats, just to make the test pass. This technique is called fake it 'till you make it. In a...