Mastering React Test-Driven Development

Second Edition

Build simple and maintainable web apps with React, Redux, and GraphQL

Daniel Irvine

BIRMINGHAM—MUMBAI

Mastering React Test-Driven Development

Second Edition

Copyright © 2022 Packt Publishing

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First published: May 2019

Second edition: September 2022

Production reference: 2130922

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ISBN 978-1-80324-712-0

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To Nige, my first mentor, who taught me the importance of slowing down.

– Daniel Irvine

Foreword

For as long as test-driven development (TDD) has existed, there has been debate over whether TDD is feasible for user interface work—even among its staunchest proponents. When people built tools to prove that it’s possible, the debate shifted to whether TDD is as valuable for UIs, considering that programmers can get rapid feedback by seeing and interacting with an interface. Even when TDD’s value is evidenced by smaller, more consistent, single-responsibility units of UI code, some would question whether the same could have been accomplished with less effort by simply following established design patterns.

Is TDD worth your time? Will it result in fewer bugs in your code? Will it improve the design of your system? Will it make future maintenance easier? Maybe.

In the fifteen-or-so years that I’ve been learning, practicing, and teaching test-driven development I have oscillated back-and-forth. Sometimes I relentlessly pursue 100% code coverage, and other times I’ll build worrisomely large applications with no automated tests at all. What I’ve found—and what might surprise some readers—is that my code basically turns out the same whether I practice TDD or not: a similar frequency of bugs, the same idiosyncratic design, and no more or less a burden to maintain.

(At this point, you’d be right to start wondering what this ambivalent foreword is doing in a book designed to teach you TDD.)

The reason that TDD itself doesn’t impact my code very much is because my years of practice have utterly and irrevocably changed me.

I write small single-purpose units, because I’ve felt the sheer exhaustion of writing tests of sprawling unfocused objects.

I avoid mixing levels of abstraction, because I’ve been hopelessly lost in mazes of mock objects that combine testing logic with specifying interactions.

I segregate code coupled to frameworks from feature logic, because I’ve contorted too many tests to fit dependencies that weren’t meant to be tested.

Rigorously practicing TDD transformed my career. Not because it’s the One True Way to program, but because it forces you to ceaselessly ask “how would we test that?” TDD is incredibly challenging at first, but patterns gradually emerge that result in easy-to-test code. And code that’s easy to test, is easy to write. And use. And maintain.

Wherever you are in your journey, I hope this book brings you closer to a similar destination.

Justin Searls VP of Engineering at Test Double

testdouble.com

Contributors

About the author

Daniel Irvine is a software consultant based in London. He works with a variety of languages including C#, Clojure, JavaScript, and Ruby. He’s a mentor and coach for junior developers and runs TDD and XP workshops and courses. When he’s not working, he spends time cooking and practicing yoga. He co-founded the Queer Code London meetup and is an active member of the European software craft community.

I would like to thank the technical reviewer of this edition of the book, Emmanuel Demey, for spotting the weakest points of the text and helping me improve them. I continue to be grateful for my friend and technical reviewer from the first edition, Raimo Radczewski, who is also the author of the expect-redux package that is used in this book.

The team at Packt has been supportive and professional throughout, giving me exactly what I needed to finish the book. For this second edition, I am thankful for the detailed and thoughtful editing that Feza Shaikh has undertaken, helping to deliver the book ahead of schedule. My technical editor, Saurabh Kadave, spotted plenty of mistakes that would have otherwise gone unnoticed. Aamir Ahmed, Bhavya Rao, and Manthan Patel were also instrumental in the production of the second edition.

From the first edition, I am thankful for the hard work of Keagan Carneiro, Sachin Sunilkumar from Packt, and also my friends and colleagues Charlotte Payne, Dan Pelensky, Isidro López, Makis Otman, Sam Szreter, Zach Shaw, Brendan Murphy, and Lucy Monie Hall.

Finally, thank you to all the readers of the first edition who took the time to send me comments and feedback, all of which were invaluable. This second edition is better because of your help.

About the reviewer

Emmanuel Demey works with the JavaScript ecosystem every day, and he spends his time sharing his knowledge with anybody. His first goal at work is to help the people that he works with. He speaks at French conferences (Devfest Nantes, Devfest Toulouse, Sunny Tech, Devoxx France, and others) about anything related to the web platform: JavaScript frameworks (Angular, React.js, Vue.js), accessibility, Nest.js, and so on. He has been a trainer for 10 years at Worldline and Zenika (two French consulting companies). He is also a co-leader of the Google Developer of Lille group and a co-organizer of the Devfest Lille conference.