Summary

Michael Feathers defines legacy code as code without tests, turning a vague complaint about inherited systems into a specific problem with a specific remedy. The difficulty he takes seriously is circular: you want tests before you change anything, but the code often cannot be tested until it is changed. The opening chapters build the tools for breaking that circle, above all the seam, a place where behavior can be substituted without editing the code there, plus ways to sense what code does and separate it from its dependencies. The bulk of the book is arranged by the question a developer arrives with, each chapter titled as the complaint itself: I cannot get this class into a test harness, I do not know what tests to write, I need to change a monster method and cannot write tests for it. A final chapter collects the dependency-breaking techniques. Examples are in Java, C++, and C#.

Target Readers

• Developers who have inherited a codebase with no tests and need to change it without a rewrite they will never be given time for
• Engineers stuck at the point where a class cannot be instantiated in a test at all, who need a technique rather than encouragement
• Teams who want a shared name for the moves they make when breaking dependencies, so the work can be discussed in review

Colophon

Publisher

Shoeisha

ISBN

978-4798116839

Published

Jul 2009

List price

¥4,620incl. taxMay differ from the actual selling price on Amazon