<pre>Author/s : Michael Feathers Publisher : Prentice Hall PTR Category :Project management, Process and Best Practices Review by : Jeanne Boyarsky Rating : 10 horseshoes</pre> "Working Effectively with Legacy Code" is a very valuable resource. The author defines "legacy code" as "code without tests." It doesn't matter whether the code was written last week or ten years ago. There is more emphasis on old code that nobody understands, mainly because it is messier and harder to work with.
The examples in the book are mainly in C, C++ and Java, but there are a couple in C# and Ruby. While it is essential to know one of these languages, the author provides enough information to understand the others. When a technique only applies to a certain language, it is clearly indicated.
The author shows how different diagrams can help you learn how to understand code. In addition to UML, there are dependency and effect sketches. The author uses these to show how to think about understanding and refactoring. Other tools, such as refactoring browsers and mocks are explained.
Speaking of refactoring, there are "dependency breaking techniques" (aka refactorings) with step-by-step instructions (Martin Fowler style) throughout the book. There are also explanations of why patterns and design rules exist. Most importantly, there are lots and lots of cross-references and an excellent index.
Working with legacy code isn't fun, but this book helps make it as painless as possible. With the split emphasis between psychological/understanding/techniques and refactoring, this book is both a great read and an excellent reference.