Essential Test-Driven Development

Rob Myers is a seasoned software developer and instructor with four decades of experience. He has trained and mentored teams worldwide in TDD and Agile practices, helping organizations of all sizes achieve lasting software excellence.

"Rob Myers's modern, practical take on TDD gets your hands dirty quickly while keeping them safe with clear rules, smart safety nets, and hard-earned wisdom from decades of real experience. Engaging, entertaining, and relevant to every developer."--Jeffrey J. Langr, veteran software developer and author"After decades of TDD, Rob delivers what we've needed--a book treating test code as a first-class citizen. His insights on test smells and AI-assisted coding give a glimpse into our future where clean test specifications replace architectural debates. Multi-language examples show TDD's universal principles. A must-have reference."--Shane Duan, Director of Engineering, Rockfish Data, Inc."Essential Test-Driven Development is a must-read for anyone who cares about writing quality, confident code. I've seen Rob's approach in action and witnessed firsthand the remarkable impact effective TDD can have. His passion, clarity, and practical guidance make this book an invaluable resource for any serious software professional."--Jorgen Hesselberg, author of Unlocking Agility; co-founder of Comparative Agility"Do you want to feel confident while you develop? Do you want to earn the trust of your colleagues and demonstrate trustworthiness to them? Here's how, from someone who has been doing it for a quarter century."--Kent Beck"Easily the best book on TDD I've seen in over a decade. Myers avoids the empty sloganeering that treats TDD as an aftermarket bolt-on to old-school approaches, and his design detours take the reader deep into the meat of the subject."--GeePaw Hill, independent software development technical coach"Rob brings Test-Driven Development back to what it truly is: a craft that connects thinking, quality, and joy. This book inspires developers and teams alike to embrace sustainable technical excellence as the foundation for meaningful, agile co-creation. Highly recommended."--Björn Jensen, CST, CTC, CEC & AKT"TDD was a steep learning curve for my teams. And once learned it gave us the unicorn magic. I love how this book lowers that learning curve. You can easily work through it with Rob as your virtual pair."--Lisa Crispin, consultant and author

• Foreword xiiiPreface xixAcknowledgments xxixAbout the Author xxxiPart I: Core Techniques 1Chapter 1: Thinking Test-Driven 3The Safety Net 4Units of Behavior 4Behavioral Boundaries 6A Taste of TDD 9The Future of Test-Driven Development 14Summary 20Chapter 2: Basic Moves 21The TDD Flowchart 21Thinking in Tests 23Three Basic Techniques 26Requests, Tasks, and a To-Do List 26Exercise Walk-Through 30Summary 45Chapter 3: Build upon Existing Behavior 47Next Steps 47Improving the Tests 53Refactoring the Tests 55Removing the Symptomless Defect 57Triangulating Away Side Effects 60A Picture Is Worth a Thousand Words 62Combining Behaviors 66Summary 71Chapter 4: Exceptional Behaviors 73Raising/Throwing 73A Test That Passes When the Code "Fails" 75External Exceptions 77Summary 78Chapter 5: Sustaining a Test-Driven Practice 79Attributes of a Good Unit Test 80Where to Start 83What to Test 88When Code Is Difficult to Test 96Test Smells and Refactorings 97Other Common Testing Challenges 136How to Test a Private Summary 138Part II: Ancillary Practices 139Chapter 6: Test Doubles 141The Trouble with Dependencies 142A Test Double Taxonomy 143Additional Recommendations 153Summary: Use with Care 160Chapter 7: Testing Legacy Code 163Characterization Testing 165Other Considerations 177Introduce Virtualizing Proxy 180Summary: The Complete Toolbox 186Part III: Return on Investment 189Chapter 8: The Black Swans 191The Agilist's Dilemma 192The Three Levels of Value 193The Black Swan User Stories 195Taming the Black Swans 204Summary 205Appendix: Exercises 207Index 213