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77 of 82 people found the following review helpful:
5.0 out of 5 stars
a wealth of practical information and solutions, October 13, 2004
Martin Fowler's book on Refactoring showed us how to improve the design of our code. We learned to make changes safely, by taking small, rote steps, and by ensuring that we ran our tests after each small change. But what if we're working on the typical ugly system with no tests? In Working Effectively With Legacy Code, Michael Feathers tackles the problem that most of us end up dealing with.
Feathers does an excellent job of articulating the problems and scenarios, using clear examples from C, C++, Java, and C#. Many of the code examples look a lot like real examples I come across all the time--they don't appear to be fabricated.
Working Effectively With Legacy Code contains a catalog that provides a wealth of solutions. The catalog shows how to resolve concerns like, "I'm changing the same code all over the place" and "how do I safely change procedural code?"
The book is highly entertaining and comes across as a conversation with a really sharp, really patient guru developer. Often, it's a chore to slog through code-heavy books. But Feathers manages to keep my attention with interesting stories, loads of examples, and well-written text.
I think that Working Effectively With Legacy Code is an important book. The vast majority of existing code presents the classic catch-22: you can't change it safely because it doesn't have tests, and you can't write tests without changing it to easily support testing. It's not an easy problem, and most people will give you high-level ideas for solving it. Feathers is the first person to dig deep and present a wealth of knowledge and insight on the problem, all in one place. I'll be pulling this book from my shelf for years to come.
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38 of 38 people found the following review helpful:
5.0 out of 5 stars
No more fairy-land, October 20, 2004
The average book on Agile software development describes a fairyland of greenfield projects, with wall-to-wall tests that run after every few edits, and clean & simple source code.
The average software project, in our industry, was written under some aspect of code-and-fix, and without automated unit tests. And we can't just throw this code away; it represents a significant effort debugging and maintaining. It contains many latent requirements decisions. Just as Agile processes are incremental, Agile adoption must be incremental too. No more throwing away code just because it looked at us funny.
Mike begins his book with a very diplomatic definition of "Legacy". I'l skip ahead to the undiplomatic version: Legacy code is code without unit tests.
Before cleaning that code up, and before adding new features and removing bugs, such code must be de-legacified. It needs unit tests.
To add unit tests, you must change the code. To change the code, you need unit tests to show how safe your change was.
The core of the book is a cookbook of recipes to conduct various careful attacks. Each presents a particular problem, and a relatively safe way to migrate the code towards tests.
Code undergoing this migration will begin to experience the benefits of unit tests, and these benefits will incrementally make new tests easier to write. These efforts will make aspects of a legacy codebase easy to change.
It's an unfortunate commentary on the state of our programming industry how much we need this book.
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32 of 33 people found the following review helpful:
5.0 out of 5 stars
excellent reference and guide, November 11, 2004
"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.
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