Test-driven development

Let us 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 we encourage you to read 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.

The developer then writes the minimal amount of code to make the test pass. When the test run 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 'til you make it. In a second iteration...