Test-Driven Development by Example

PinglePongle writes "Kent Beck is well known as one of the main drivers behind eXtreme Programming -- a style of development which favours a very disciplined but low-formality approach to coding. Writing applications 'test-first' is one of the practices of XP, and this book explores the subject of test-driven development in detail." Read on for the complete review. Test-Driven Development by Example author Kent Beck pages 220 publisher Addison Wesley rating Superb reviewer PinglePongle ISBN 0321146530 summary Kent Beck -- author of the original Extreme Programming book -- explains in detail how to turn your development world upside down by starting with the test, then writing the code.

What it's all about: Test-driven development is about being able to take tiny little steps forward, test that the step took you in the right direction, and repeat. The "TDD Mantra" is red/green/refactor:

• Red: write a test which will exercise a feature, but which will fail (because you haven't yet written the code)
• Green: make the test succeed, doing whatever you need to do to get to "green" as quickly as possible -- don't worry about prettiness
• Refactor: now that you have code which passes the test, eliminate all the duplication

The book then shows 2 fairly detailed examples of a development project (or snippet of a project) which progress using this style of coding. The first example deals with the creation of multi-currency capabilities for an existing project. In the space of 17 chapters, the author walks you through the creation of 6 classes (1 test class, 5 functional classes), complete with the thought-processes behind them. The code is written in java, and is trivially easy to follow, because it gets introduced in tiny little chunks; most chapters are less than 6 pages in length.

The second example is the creation of a unit testing framework in Python. It is significantly more complex and real-world than the first example, but again proceeds in very small steps, and in small chapters.

The final part of the book contains patterns for test-driven development -- practical real-world advice on how to do this stuff for real. Nearly all the "patterns" are phrased as question/answer pairs, and they range from deeply technical design patterns to advice on the best way to arrange the furniture.

What's good about the book? Kent Beck is a very good writer -- his writing is clear, he is not afraid to leave out stuff he assumes you can guess for yourself, but when he does go into detail you feel it is necessary to get the big picture, rather than mere geek bravado. Even if you don't adopt Test-Driven Development, many of the ideas are well worth considering for your day-to-day coding situations.

What could have been better? The book stresses the importance of taking 'little steps,' and sometimes you feel impatient to move to more challenging tests before properly finishing the current chapter. I was also hoping for more of a discussion on the practicalities of unit testing database-driven systems, where you frequently have to test business entities which are closely coupled to the database.

Summary If you code for a living, or manage people who do, you should read this book -- it's a quick enough read -- and consider some of the assertions it makes. If you feel you're introducing more bugs than you expected, if you feel uneasy about how close your work matches the requirements, this book gives you some powerful ideas. You can purchase Test-Driven Development by Example from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

Opinion on Boost:'s unit test framework

[Eponymous Coward]

Okay- this is a bit off-topic, but thought someone here might have some experience with the unit test stuff inside of Boost.

I'm wondering if anybody has used the Boost framework for something more than a toy program. It seems well though out (like all of the stuff in Boost), but I just don't have any experience with unit test stuff. I have nothing to compare it to.

-ec