Graham Lee - Test-Driven iOS Development

Graham Lee

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This book is for anyone who has ever shipped a bug. Youre
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My experience of telling other developers about test-driven development for Objective-C came about almost entirely by accident. I was scheduled to talk at a conference on a different topic, where a friend of mine was talking on TDD. His wife had chosen (I assume thats how it works; Im no expert) that weekend to give birth to their twins, so Chuckwho commissioned the book you now hold in your handsasked me if I wouldnt mind giving that talk, too. Thus began the path that led ultimately to the year-long project of creating this book.

Its usually the case that reality is not nearly as neat as the stories we tell each other about reality. In fact, I had first encountered unit tests a number of years previously. Before I was a professional software engineer, I was a tester for a company whose product was based on GNUstep (the Free Software Foundations version of the Cocoa libraries for Linux and other operating systems). Unit testing, I knew then, was a way to show that little bits of a software product worked properly, so that hopefully, when they were combined into big bits of software, those big bits would work properly, too.

I took this knowledge with me to my first programming gig, as software engineer working on the Mac port of a cross-platform security product. (Another simplificationI had, a few years earlier, taken on a six-week paid project to write a LISP program. Weve all done things were not proud of.) While I was working this job, I went on a TDD training course, run by object-oriented programming conference stalwart Kevlin Henney, editor of 97 Things Every Programmer Should Know, among other things. It was here that I finally realized that the point of test-driven development was to make me more confident about my code, and more confident about changing my code as I learned more. The time had finally arrived where I understood TDD enough that I could start learning from my own mistakes, make it a regular part of my toolbox, and work out what worked for me and what didnt. After a few years of that, I was in a position where I could say yes to Chucks request to give the talk.

Its my sincere hope that this book will help you get from discovering unit testing and test-driven development to making it a regular part of how you work, and that you get there in less time than the five years or so it took me. Plenty of books have been written about unit testing, including by the people who wrote the frameworks and designed the processes. These are good books, but they dont have anything specifically to say to Cocoa Touch developers. By providing examples in the Objective-C language, using Xcode and related tools, and working with the Cocoa idioms, I hope to make the principles behind test-driven development more accessible and more relevant to iOS developers.

Ah, yesthe tools. There are plenty of ways to write unit tests, depending on different features in any of a small hoard of different tools and frameworks. Although Ive covered some of those differences here, I decided to focus almost exclusively on the capabilities Apple supplies in Xcode and the OCUnit framework. The reason is simply one of applicability; anyone whos interested in trying out unit tests or TDD can get on straight away with just the knowledge in this book, the standard tools, and a level of determination. If you find aspects of it lacking or frustrating, you can, of course, investigate the alternatives or even write your ownjust remember to test it!