Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle: first the developer writes an (initially failing) automated test case that defines a desired improvement or new function, then produces the minimum amount of code to pass that test, and finally refactors the new code to acceptable standards.

The following sequence of steps is generally followed:

• Add a test
• Run all tests and see if the new one fails
• Write some code
• Run tests
• Refactor code
• Repeat

There’s a plenty of articles written on TDD and Wikipedia is always a good start. This article will focus on the actual test and implementation using variation of one of the Roy Osherove Katas. Do not click the link until you’re finished with this article. This excercise is best done when not all requirements are known in advance.

Below you will find the test code related to each requirement and afterwards the actual implementation. Try to read only one requirement, write the tests and the implementation yourself and compare it with the results from this article. Remember that there are many different ways to write tests and implementation. This article is only one out of many possible solutions.

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