Test-Driven Development: A Practical Guide (Coad Series) (Paperback)

The book falls short of these goals: The explanations about writing tests are short on advice and are sometimes misleading. The presentation of the tools is long, with little useful facts.

The book is organized into four parts: Background on TDD, refactoring and programming by intention; A look at JUnit and related tools used to write and run tests; A lengthy example of TDD; An overview of other tools in the xUnit family. The book is targeted at a Java audience but programmers using other languages should have little difficulties understanding the code.

I have a major problem with the background section. The author repeatedly claims that TDD provides exhaustive test coverage and ensures that you can refactor your code with confidence. Any error will be caught by the tests. This is foolish. First, tests rarely reach 100% code coverage. Even the sample that the author provides in the book ends up with less than 90% coverage. This leaves many gaps where tests will fail to detect errors. Even if tests cover 100% branches in the code tests are not exhaustive. Depending on the data used, the same branch may exhibit different behavior. (Not to speak about race conditions and other sources of hard to find bugs.) I fully agree with the author that writing unit tests will improve the quality of the code and help find bugs. But claiming that this is a silver bullet is not wise. I would recommend reading books about tests (e.g., Myers' The Art of Software Testing and McConnell's Code Complete chapter on unit testing) in addition to this book. The section on refactoring is a summary of Martin Fowler's Refactoring book which I recommend.

The second part presents JUnit. JUnit is a framework used to write and run tests. It is a good presentation. However I would have liked to get pieces of advices on what tests to write in addition to how to write them. The author briefly mentions boundary testing but does not have much to say about the tests themselves. Again a test book is invaluable for this. The author recommends using a test coverage tool as well as Jester to measure the tests coverage. This is a great idea.

The third section is an (overly) extended example: the author walks us through writing TDD code. This could have been a great part, giving meaning to the `practical' adjective in the book title. Unfortunately it is a long rambling, showing lots of code but short on insights. The actual `meat' of this part could be summarized in less than five pages.

The last section presents variations on the JUnit tool. Many languages (C++, C#, VB, Python, etc) are discussed. This part would have been better put on a website rather than printed in the book. Given the changes in some of these frameworks the information is obsolete.

The books ends with several appendices dealing with extreme programming and agile modeling.

Unit tests are a great tool to improve code quality. Whether or not you actively practice TDD, a good book on it can provide insights into improving your code. This book contains some interesting bits of wisdom. However much of it is buried by the rest of the material.

The only thing this book is missing, I think, is a discussion about data setup and database-related testing, dbUnit, etc., other than an advice to avoid it altogether (p. 83). While you can indeed use mocks to avoid it, on the large real projects some kind of integration testing (including testing with the database) will be necessary. I hope the second edition will come out at some point!

Overall, it's a great book for both newcomers and developers with unit testing experience. BTW, it won SD West 2004 Jolt Award.

The book first touches on some topics fundamental to TDD, such as refactoring, programming by intention, and of course the basic theory behind TDD. Appendices further flesh out this material by addressing extreme programming and agile modeling.

Although other members of the xUnit family are looked at, this book is squarely focused on JUnit and Java. As such, the text goes into detail about using JUnit, including the API, and how to go about the task of writing tests. Along with the JUnit coverage, the reader is presented with information on several JUnit extensions and JUnit related tools designed to aid the TDD process. Where this book really shines is in its coverage of mock objects and techniques for testing GUIs within JUnit.

The meat of this book rests in a very detailed walkthrough of a project using TDD. Astels leads the reader through every test and every refactoring along the way, from inception to the finished product. This is probably the next best thing to sitting down for a pair-programming session with a TDD guru.

Unfortunately, there are a couple of complaints I feel the need to point out. The project presented is a Swing application that persists its data in a flat file. There is no coverage provided for testing web based enterprise applications. While mention is made of DatabaseChecker, a test utility suitable for simple database tests, Astels chose not to have the example project use a database for persistence. As a consequence of this decision, this common task is left unaddressed.

Despite these omissions, there is still much to be gained from this book. I feel a reader may obtain the most benefit by downloading the sample code and working through the example project step-by-step along with the text. If you are interested in a practical guide to TDD, this book is definitely worth a look.