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What Readers Are Saying About
The RSpec Book: Behaviour-Driven Development with
RSpec, Cucumber, and Friends
The RSpec Book is a fantastic introduction to all things BDD. It goes
much deeper than just testing to provide you with the right tools you
need to fully embrace the ideas that the framework has baked in.
Aaron Bedra, principal, Relevance Inc.
This book covers the territory of writing great software, and the
authors are your experienced guides. If you follow the map that they
have drawn, you’ll learn to write only the code that you need, and
you’ll write it simply and clearly. You’ll come home from this journey
with some experiences that will have immediate and lasting effects on
the code in your editor and the code yet to flow from your fingertips.
Craig Demyanovich, 8th Light, Inc.
The RSpec Book teaches you much more than how to use RSpec’s features; it teaches you how to write code the way the RSpec team does:
patiently, and with great precision and clarity. There is something
here for everyone: beginners are given plenty of gentle attention but
there is some real meat for the more experienced reader to chew on,
too.
Matt Wynne, independent programmer and coach
The second generation of tools for the XP generation explained by their
creators and maintainers. Awesome, a must read.
Marcus Ahvne, software developer, Valtech
Some authors would be satisfied with just writing the definitive guide
for a technology. These folks go a step further, and show you insider
tips that will keep your tests clean and maintainable.
Ian Dees, Software Engineer
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The RSpec Book
Behaviour-Driven Development
with RSpec, Cucumber, and Friends
David Chelimsky
with Dave Astels
Zach Dennis
Aslak Hellesøy
Bryan Helmkamp
Dan North
The Pragmatic Bookshelf
Raleigh, North Carolina Dallas, Texas
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Many of the designations used by manufacturers and sellers to distinguish their products are claimed as trademarks. Where those designations appear in this book, and The
Pragmatic Programmers, LLC was aware of a trademark claim, the designations have
been printed in initial capital letters or in all capitals. The Pragmatic Starter Kit, The
Pragmatic Programmer, Pragmatic Programming, Pragmatic Bookshelf and the linking g
device are trademarks of The Pragmatic Programmers, LLC.
Every precaution was taken in the preparation of this book. However, the publisher
assumes no responsibility for errors or omissions, or for damages that may result from
the use of information (including program listings) contained herein.
Our Pragmatic courses, workshops, and other products can help you and your team
create better software and have more fun. For more information, as well as the latest
Pragmatic titles, please visit us at http://www.pragprog.com.
The team that produced this book includes:
Editor: Jacquelyn Carter
Indexing: Potomac Indexing, LLC
Copy edit: Kim Wimpsett
Layout: Steve Peter
Production: Janet Furlow
Customer support: Ellie Callahan
International: Juliet Benda
Copyright © 2010 David Chelimsky, Dave Astels, Zach Dennis, Aslak Hellesøy, Bryan
Helmkamp, and Dan North.
All rights reserved.
No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form, or by any means, electronic, mechanical, photocopying, recording, or
otherwise, without the prior consent of the publisher.
Printed in the United States of America.
ISBN-10: 1-934356-37-9
ISBN-13: 978-1-934356-37-1
Printed on acid-free paper.
P1.0 printing, December 2010
Version: 2010-11-24
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Contents
Foreword 11
About the Authors 14
Acknowledgments 16
Preface 18
Ruby and Gem Versions . . . . . . . . . . . . . . . . . . . . 18
Downloading the Code Examples . . . . . . . . . . . . . . . 19
What’s in This Book . . . . . . . . . . . . . . . . . . . . . . 19
I Getting Started with RSpec and Cucumber 21
1 Introduction 22
1.1 Test-Driven Development: Where It All Started . . . 22
1.2 Behaviour-Driven Development: The Next Step . . . 24
1.3 RSpec . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.4 Cucumber . . . . . . . . . . . . . . . . . . . . . . . . 26
1.5 The BDD Cycle . . . . . . . . . . . . . . . . . . . . . . 28
2 Hello 30
2.1 Installation . . . . . . . . . . . . . . . . . . . . . . . . 30
2.2 Hello RSpec . . . . . . . . . . . . . . . . . . . . . . . 31
2.3 Hello Cucumber . . . . . . . . . . . . . . . . . . . . . 33
3 Describing Features 37
3.1 Introducing Codebreaker . . . . . . . . . . . . . . . . 38
3.2 Planning the First Release . . . . . . . . . . . . . . . 38
3.3 Planning the First Iteration . . . . . . . . . . . . . . 44
3.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 52
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CONTENTS 6
4 Automating Features with Cucumber 53
4.1 Steps and Step Definitions . . . . . . . . . . . . . . . 55
4.2 Step Definition Methods . . . . . . . . . . . . . . . . 56
4.3 Test Double . . . . . . . . . . . . . . . . . . . . . . . 60
4.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 62
5 Describing Code with RSpec 63
5.1 Getting Started with RSpec . . . . . . . . . . . . . . 63
5.2 Red: Start with a Failing Code Example . . . . . . . 66
5.3 Green: Get the Example to Pass . . . . . . . . . . . . 68
5.4 Refactor . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.5 What We’ve Learned . . . . . . . . . . . . . . . . . . . 76
6 Adding New Features 77
6.1 Scenario Outlines in Cucumber . . . . . . . . . . . . 77
6.2 Responding to Change . . . . . . . . . . . . . . . . . 80
6.3 What We’ve Learned . . . . . . . . . . . . . . . . . . . 83
7 Specifying an Algorithm 84
7.1 Begin with the Simplest Example . . . . . . . . . . . 84
7.2 Refactor to Remove Duplication . . . . . . . . . . . . 88
7.3 Refactor to Express Intent . . . . . . . . . . . . . . . 89
7.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 94
8 Refactoring with Confidence 96
8.1 Sniffing Out Code Smells . . . . . . . . . . . . . . . . 96
8.2 One Step at a Time . . . . . . . . . . . . . . . . . . . 98
8.3 Updating Specs After Refactoring . . . . . . . . . . . 107
8.4 Exploratory Testing . . . . . . . . . . . . . . . . . . . 111
8.5 What We’ve Learned . . . . . . . . . . . . . . . . . . . 112
9 Feeding Back What We’ve Learned 114
9.1 Use Cucumber for Collaboration . . . . . . . . . . . 114
9.2 Experimenting with a New Implementation . . . . . 118
9.3 What We’ve Learned . . . . . . . . . . . . . . . . . . . 122
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CONTENTS 7
II Behaviour-Driven Development 124
10 The Case for BDD 125
10.1 How Traditional Projects Fail . . . . . . . . . . . . . 125
10.2 Why Traditional Projects Fail . . . . . . . . . . . . . 126
10.3 Redefining the Problem . . . . . . . . . . . . . . . . . 130
10.4 The Cost of Going Agile . . . . . . . . . . . . . . . . . 133
10.5 What We’ve Learned . . . . . . . . . . . . . . . . . . . 136
11 Writing Software That Matters 138
11.1 A Description of BDD . . . . . . . . . . . . . . . . . . 138
11.2 The Principles of BDD . . . . . . . . . . . . . . . . . 138
11.3 The Project Inception . . . . . . . . . . . . . . . . . . 139
11.4 The Cycle of Delivery . . . . . . . . . . . . . . . . . . 141
11.5 What’s in a Story? . . . . . . . . . . . . . . . . . . . . 145
11.6 What We’ve Learned . . . . . . . . . . . . . . . . . . . 148
III RSpec 149
12 Code Examples 150
12.1 Describe It! . . . . . . . . . . . . . . . . . . . . . . . . 151
12.2 Pending Examples . . . . . . . . . . . . . . . . . . . . 155
12.3 Hooks: Before, After, and Around . . . . . . . . . . . 158
12.4 Helper Methods . . . . . . . . . . . . . . . . . . . . . 162
12.5 Shared Examples . . . . . . . . . . . . . . . . . . . . 164
12.6 Nested Example Groups . . . . . . . . . . . . . . . . 166
12.7 What We’ve Learned . . . . . . . . . . . . . . . . . . . 169
13 RSpec::Expectations 170
13.1 should, should_not, and matchers . . . . . . . . . . 171
13.2 Built-in Matchers . . . . . . . . . . . . . . . . . . . . 172
13.3 Predicate Matchers . . . . . . . . . . . . . . . . . . . 180
13.4 Be True in the Eyes of Ruby . . . . . . . . . . . . . . 181
13.5 Have Whatever You Like . . . . . . . . . . . . . . . . 182
13.6 Operator Expressions . . . . . . . . . . . . . . . . . . 186
13.7 Generated Descriptions . . . . . . . . . . . . . . . . . 187
13.8 Subjectivity . . . . . . . . . . . . . . . . . . . . . . . . 188
13.9 What We’ve Learned . . . . . . . . . . . . . . . . . . . 190
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CONTENTS 8
14 RSpec::Mocks 191
14.1 Test Doubles . . . . . . . . . . . . . . . . . . . . . . . 192
14.2 Method Stubs . . . . . . . . . . . . . . . . . . . . . . 193
14.3 Message Expectations . . . . . . . . . . . . . . . . . 195
14.4 Test-Specific Extensions . . . . . . . . . . . . . . . . 197
14.5 More on Method Stubs . . . . . . . . . . . . . . . . . 201
14.6 More on Message Expectations . . . . . . . . . . . . 203
14.7 When to Use Test Doubles and Test-Specific Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
14.8 Risks and Trade-Offs . . . . . . . . . . . . . . . . . . 218
14.9 Choosing Other Test Double Frameworks . . . . . . 220
14.10 What We’ve Learned . . . . . . . . . . . . . . . . . . . 222
15 Tools and Integration 224
15.1 The rspec Command . . . . . . . . . . . . . . . . . . 224
15.2 TextMate . . . . . . . . . . . . . . . . . . . . . . . . . 229
15.3 Autotest . . . . . . . . . . . . . . . . . . . . . . . . . . 230
15.4 Rake . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
15.5 RCov . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
15.6 What We’ve Learned . . . . . . . . . . . . . . . . . . . 233
16 Extending RSpec 234
16.1 Metadata . . . . . . . . . . . . . . . . . . . . . . . . . 234
16.2 Configuration . . . . . . . . . . . . . . . . . . . . . . 235
16.3 Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . 235
16.4 Extension Modules . . . . . . . . . . . . . . . . . . . 238
16.5 Global Hooks . . . . . . . . . . . . . . . . . . . . . . . 239
16.6 Mock Framework . . . . . . . . . . . . . . . . . . . . 239
16.7 Custom Matchers . . . . . . . . . . . . . . . . . . . . 240
16.8 Macros . . . . . . . . . . . . . . . . . . . . . . . . . . 244
16.9 Custom Formatters . . . . . . . . . . . . . . . . . . . 247
16.10 What We’ve Learned . . . . . . . . . . . . . . . . . . . 250
IV Cucumber 251
17 Intro to Cucumber 252
17.1 From 20,000 Feet . . . . . . . . . . . . . . . . . . . . 253
17.2 Features . . . . . . . . . . . . . . . . . . . . . . . . . 253
17.3 Customer Acceptance Tests . . . . . . . . . . . . . . 257
17.4 Gherkin . . . . . . . . . . . . . . . . . . . . . . . . . . 257
17.5 Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . 259
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CONTENTS 9
17.6 Steps . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
17.7 The cucumber Command . . . . . . . . . . . . . . . 261
17.8 Given/When/Then . . . . . . . . . . . . . . . . . . . 262
17.9 Declarative and Imperative Scenario Styles . . . . . 263
17.10 Organizing Features . . . . . . . . . . . . . . . . . . 264
17.11 Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
17.12 What We’ve Learned . . . . . . . . . . . . . . . . . . . 267
18 Cucumber Detail 269
18.1 Step Definitions . . . . . . . . . . . . . . . . . . . . . 269
18.2 World . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
18.3 Calling Steps Within Step Definitions . . . . . . . . 272
18.4 Hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
18.5 Background . . . . . . . . . . . . . . . . . . . . . . . 275
18.6 Multiline Text . . . . . . . . . . . . . . . . . . . . . . 276
18.7 Tables in Steps . . . . . . . . . . . . . . . . . . . . . 277
18.8 Scenario Outlines . . . . . . . . . . . . . . . . . . . . 278
18.9 Configuration . . . . . . . . . . . . . . . . . . . . . . 280
18.10 What We’ve Learned . . . . . . . . . . . . . . . . . . . 280
V Behaviour-Driven Rails 282
19 BDD in Rails 283
19.1 Outside-In Rails Development . . . . . . . . . . . . . 284
19.2 Setting Up a Rails 3 Project . . . . . . . . . . . . . . 286
19.3 Setting Up a Rails 2 Project . . . . . . . . . . . . . . 289
19.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 289
20 Cucumber with Rails 290
20.1 Step Definition Styles . . . . . . . . . . . . . . . . . . 290
20.2 Direct Model Access . . . . . . . . . . . . . . . . . . . 292
20.3 What We’ve Learned . . . . . . . . . . . . . . . . . . . 297
21 Simulating the Browser with Webrat 298
21.1 Writing Simulated Browser Step Definitions . . . . . 299
21.2 Navigating to Pages . . . . . . . . . . . . . . . . . . . 304
21.3 Manipulating Forms . . . . . . . . . . . . . . . . . . 308
21.4 Specifying Outcomes with View Matchers . . . . . . 313
21.5 Building on the Basics . . . . . . . . . . . . . . . . . 316
21.6 What We’ve Learned . . . . . . . . . . . . . . . . . . . 319
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CONTENTS 10
22 Automating the Browser with Webrat and Selenium 320
22.1 Getting Started . . . . . . . . . . . . . . . . . . . . . 321
22.2 Writing Step Definitions for Selenium . . . . . . . . 324
22.3 Debugging Selenium Issues . . . . . . . . . . . . . . 328
22.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 330
23 Rails Views 331
23.1 Writing View Specs . . . . . . . . . . . . . . . . . . . 331
23.2 Mocking Models . . . . . . . . . . . . . . . . . . . . . 334
23.3 Specifying Helpers . . . . . . . . . . . . . . . . . . . . 341
23.4 When Should I Write View Specs? . . . . . . . . . . . 343
23.5 What We’ve Learned . . . . . . . . . . . . . . . . . . . 343
24 Rails Controllers 345
24.1 Controller Specs . . . . . . . . . . . . . . . . . . . . . 345
24.2 Context-Specific Examples . . . . . . . . . . . . . . . 352
24.3 Specifying ApplicationController . . . . . . . . . . . 361
24.4 What We’ve Learned . . . . . . . . . . . . . . . . . . . 363
25 Rails Models 365
25.1 Writing Model Specs . . . . . . . . . . . . . . . . . . 365
25.2 Specifying Business Rules . . . . . . . . . . . . . . . 373
25.3 Exercise . . . . . . . . . . . . . . . . . . . . . . . . . . 382
25.4 Useful Tidbits . . . . . . . . . . . . . . . . . . . . . . 383
25.5 What We’ve Learned . . . . . . . . . . . . . . . . . . . 386
A RubySpec 388
A.1 The Project . . . . . . . . . . . . . . . . . . . . . . . . 389
A.2 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . 389
A.3 Guards . . . . . . . . . . . . . . . . . . . . . . . . . . 391
A.4 Extensibility . . . . . . . . . . . . . . . . . . . . . . . 392
A.5 MSpec . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
A.6 Tags . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394
A.7 Community . . . . . . . . . . . . . . . . . . . . . . . . 395
B RSpec’s Built-in Expectations 397
C Bibliography 401
Index 403
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Foreword
Caution! You’ve fallen for a trap. You’ve picked up this book thinking it
was about RSpec. Fortunately, you decided to read the foreword. Good!
That gives me the opportunity to tell you about the mistake you just
made and possibly save you from an unexpected fate.
You see, this book isn’t about RSpec at all. Oh, RSpec is certainly mentioned. There are lots of examples of how to use it. There’s even a very
detailed reference manual in Part III. But that’s all just part of an insidiously clever deception, because this book is not about RSpec.
Perhaps you thought you might read about Cucumber? After all, Part
IV is named “Cucumber.” Oh, these authors are clever; God they are!
They’ve littered this book with examples and details that tell you all
about Cucumber in all its intricacies and all its copious fiddledy-bits.
There’s even a section on using it with Rails and Webrat and all the
other gory things that you’ll need to become a Cucumber expert. But
this book is not about Cucumber.
No. This book is not about RSpec. And this book is not about Cucumber. This book is about. . .
I’m not sure I should tell you. I mean, once the secret gets out, it’s liable
to cause mayhem. If it ever got out who the audience for this book really
is, if the masses learned of the diabolical plan being executed in their
midst, I’m not sure our civilization would survive.
You see. . . (come closer, and cover this part with your hand so nobody
else can see it). . . you see, this book is not for. . . (covered?). . . it’s not for
Ruby programmers!
There, I’ve said it! Now don’t panic, and don’t drop the book—whatever
you do, don’t drop the book! Hold on tight, and keep it covered. Don’t
let anyone else see.
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FOREWORD 12
Yes, you see, this book is not about RSpec. It’s not about Cucumber, It’s
not for Ruby programmers. This book is for. . . (covered again?). . . it’s for
all programmers!
Keep a good tight grip. I know it’s hard. Don’t look around suspiciously.
Don’t draw attention to yourself. Just try to stay calm, breathe normally, and keep reading.
Yes, all the code is in Ruby. Yes, all the examples use RSpec and
Cucumber to one degree or another. Yes, if you read this book, you will
learn RSpec, Cucumber, and things about Ruby and Rails and Webrat
that you didn’t know before. No doubt about it. Remember, the best lies
are near-truths.
Here’s the thing. While you read this book, you will think you are
learning about all those cool tools. You will think “Oh, cool, I’m learning RSpec and Cucumber.” But you will be learning something else at
the same time! Something unexpected. Something unadvertised. Something, perhaps, unwelcome.
As you read these pages, a hidden meme will creep into your mind—a
meme of such potency and power that it is likely to change everything
about the way you program. And not just how you program in Ruby!
If you read this book, that meme will change the way you program
in Java, C#, Python, or (oh, God, the thought) COBOL! This book will
change the way you code—period!
Worse, you don’t have to be a Ruby programmer to be infected by this
meme. As I said, these authors are clever. Their unholy plan is to infect
all programmers with this meme. You see, they’ve cleverly constructed
the Ruby code in this book so that it can be understood by (gasp) any
programmer at all! I mean, this is worse than Fluoridation!
Any programmer who picks up this book will be infected by the meme.
And the meme is subtle. And the meme is persistent. And the meme
will have its way. And when it does, our industry will never be the same
again. Are you willing to risk that?
What is this meme? What name shall we give it? The meme is legion!
It’s not just Agile, though Agile is there. It’s not just TDD and BDD,
though both are there. It’s not just Continuous Integration, Acceptance Test–Driven Development, Acceptance Test–Driven Planning, or
even Extreme Programming, though all those things are present in the
meme.
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FOREWORD 13
No, the meme is more than any one of those things. The meme is a
synergistic witches brew of some of the most contagious and effective
ideas of the past two decades. The meme is. . .
Dare I say it?
The meme is. . .
. . . Craftsmanship.
—Robert C. Martin
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About the Authors
David Chelimsky is the lead developer/maintainer of RSpec, and has
contributed to several other open source projects including Cucumber,
Aruba, and Rails. He has been developing software for over a decade,
including three years training and mentoring agile teams at Object
Mentor. He is currently a Senior Software Engineer at DRW Trading
Group in Chicago, IL. In his spare time, David likes to play guitar,
travel, and speak something resembling Portuguese.
Dave Astels is the Director of Technology at ChannelFireball.com and
has been involved with software and computing for over 25 years,
recently having spent several years working exclusively with Ruby and
Rails. Dave wrote the article that prompted Steven Baker to start the
RSpec project.
Zach Dennis is a co-founder and fellow human at Mutually Human
Software, an expert custom software strategy and design consultancy
in Grand Rapids, Michigan. He has been enjoying Ruby for nearly eight
years and has contributed to several projects such as Ruby’s standard
library documentation, Ruby on Rails, and RSpec. In his spare time,
Zach loves spending time with his family, continuously learning, playing music, and running continuousthinking.com.
Aslak Hellesøy is a Senior Software Engineer at DRW Trading Group
in London. While contributing to this book he was the Chief Scientist
of BEKK Consulting in Oslo. In 2003, after seven years of professional
Java programming, he fell in love with Ruby. He has contributed to
dozens of open source projects and is the founder of the Cucumber
project. Aslak likes to cook, ski, and travel.
Bryan Helmkamp maintains Webrat, a Ruby library to implement acceptance tests for web applications in an expressive and maintainable
way, and is an active participant in the New York City Ruby community. Bryan is the CTO of Efficiency 2.0, a startup that helps people
understand and reduce their energy use.
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ABOUT THE AUTHORS 15
Dan North writes software and coaches teams and organizations in
agile and lean methods. He believes that most problems that teams face
are about communication and understanding, which is why he puts so
much emphasis on “getting the words right.” In 2003–4 this led him to
develop the ideas that would become Behaviour-Driven Development.
He is delighted by the community that has grown up around RSpec
and Cucumber, and especially the enthusiasm and dedication of their
core contributors. Dan is currently a Senior Software Engineer at DRW
Trading Group in London, where he gets to actually code again!
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