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Michael C. Feathers
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.
Take Ruby development to the next level: leverage Ruby's full power to write more maintainable, manageable, and pleasing applications * *Master object-oriented Ruby techniques for building applications that are as easy to maintain and upgrade as they were to write! *Discover concrete solutions for common issues associated with poorly designed, hard-to-change Ruby applications. *Solves painful problems now facing many of the world's 1+ million Ruby developers, including programmers at all levels of experience. Years after the initial release of Ruby on Rails, the chickens are coming home to roost. Suddenly, anyone could write a web application -- and it seems like everyone did. The web is now awash in Ruby applications that were easy to write but are now virtually impossible to change, extend, or grow. This book solves that problem by teaching developers real-world object oriented design techniques specifically focused on Ruby. Writing for more than 1,000,000 Ruby developers at all levels of experience, Sandi Metz shares knowledge and concrete solutions for creating more extensible, more maintainable applications - and for fixing many of the poorly designed applications they must now manage. The first book to focus squarely on object-oriented Ruby application design, Practical Object Oriented Design in Ruby will guide developers to superior outcomes, even if their previous experience has been strictly limited to 'procedural' techniques. Metz distills a lifetime of conversations about object-oriented design and many years of whiteboard drawings into a set of specific Ruby practices and patterns that lead to more manageable and pleasing code. Novice Ruby programmers will find specific 'rules to live by'; intermediate Ruby programmers will find valuable principles they can flexibly interpret and apply; and advanced Ruby programmers will find a common language they can use to lead development and guide their colleagues.