The Cucumber Book: Behaviour-Driven Development for Testers and Developers (Pragmatic Programmers)

328 Pages·2012·6.66 MB·English

by  Matt Wynne

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What Readers Are Saying About
The Cucumber Book
Few tools have managed to bridge the developer-customer divide as well as
Cucumber has. Cucumber is not a tool for testing applications. Cucumber is a
philosophy for communicating requirements. This book brings that philosophy
to life.
➤ Robert C. Martin (Uncle Bob)
I devoured the Cucumber book on a train ride from Grenoble to Brussels a few
days after watching Matt’s presentation “BDD As It’s Meant to Be Done.” These
two resources helped me understand in just a few hours how to avoid dozens of
common mistakes writing scenarios in the Cucumber style. It’s as though I received
an injection of perhaps two years of experience writing scenarios poorly so that I
didn’t have to go through it all myself. What a gift. I recommend this book to
everyone working with Cucumber.
➤ J. B. Rainsberger
Author, JUnit Recipes
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Teams can use Cucumber to get a better understanding of what software to build
for their customers. In this book, Aslak and Matt do a brilliant job explaining how
you get started with Cucumber with plenty of easy-to-follow examples.
➤ Rachel Davies
Author, Agile Coaching
To those of you wondering how to use Cucumber effectively, The Cucumber Book
is the answer. Not content to write just a testing book, Aslak and Matt have packed
it with practical insights on many aspects of software development. Studying this
book will make you a better software developer.
➤ Pat Maddox, B.D.D.M.F.
RSpec Core team
This is a much-needed book, providing not only an expanded description of how
to use Cucumber but an opinionated one to suggest how to use it for the best effect.
Reading this book is like having Aslak and Matt sitting next to you, patiently
helping you through your first project with Cucumber. Not only will you learn
effective use of Cucumber, but you’ll also be introduced to several other Ruby
tools that can be used with Cucumber.
➤ George Dinwiddie
Software development coach at iDIA Computing, LLC
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Matt and Aslak show you how Cucumber can save you from stale documentation,
unclear requirements, and absentee tests. By the end of the book, your team’s
programmers, testers, and product owners will be talking excitedly about the next
great product you’re going to build together.
➤ Ian Dees
Author, Scripted GUI Testing with Ruby
This book had me at “Cucumber is designed to help build bridges between the
technical and nontechnical members of a software team.” Wynne and Hellesøy
understand the whole-team approach to specification by example, with diverse
team members collaborating to deliver what the customer really wants. They use
examples to teach us how to automate regression checks with Cucumber, use it
to build a safety net to allow refactoring, and free testers to contribute their most
valuable skills to the team.
➤ Lisa Crispin
Author, Agile Testing: A Practical Guide for Testers (with Janet Gregory)
This book is a tale of how to do effective acceptance testing, with Cucumber as
the filling in the sandwich. The authors don’t just scratch the surface; they get
right under the skin and show us how versatile Cucumber can be.
➤ Robert Chatley
Principal, Devlogical
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Lots of great tips for Cucumber newbies and experts alike—Matt and Aslak have
done a great job of explaining everything from getting started to how to get the
most out of Cucumber. You’ll want to read this book cover to cover and keep it
close as a reference!
➤ Gojko Adzic
Author, Specification by Example and Bridging the Communication Gap
The Cucumber Book is a must-read for anyone thinking about using Cucumber;
it is scattered with treasures for even the most experienced Cucumber users.
➤ Antony Marcano
RiverGlide
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The Cucumber Book
Behaviour-Driven Development
for Testers and Developers
Matt Wynne
Aslak Hellesøy
The Pragmatic Bookshelf
Dallas, Texas • Raleigh, North Carolina
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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, PragProg and the linking g device are trade-
marks 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://pragprog.com.
The team that produced this book includes:
Jackie Carter (editor)
Potomac Indexing, LLC (indexer)
Kim Wimpsett (copyeditor)
David J Kelly (typesetter)
Janet Furlow (producer)
Juliet Benda (rights)
Ellie Callahan (support)
Copyright © 2012 Pragmatic Programmers, LLC.
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-13: 978-1-934356-80-7
Printed on acid-free paper.
Book version: P1.0—January 2012
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Contents
Foreword . . . . . . . . . . . . . xiii
Acknowledgments . . . . . . . . . . . xv
Preface . . . . . . . . . . . . . . xvii
Part I — Cucumber Fundamentals
1. Why Cucumber? . . . . . . . . . . . . 3
1.1 Automated Acceptance Tests 4
1.2 Behaviour-Driven Development 4
1.3 Living Documentation 6
1.4 How Cucumber Works 7
1.5 What We Just Learned 8
2. First Taste . . . . . . . . . . . . . 11
2.1 Understanding Our Goal 11
2.2 Creating a Feature 12
2.3 Creating Step Definitions 14
2.4 Implementing Our First Step Definition 16
2.5 Running Our Program 17
2.6 Changing Formatters 18
2.7 Adding an Assertion 19
2.8 Making It Pass 20
2.9 What We Just Learned 23
3. Gherkin Basics . . . . . . . . . . . . 25
3.1 What’s Gherkin For? 25
3.2 Format and Syntax 28
3.3 Feature 29
3.4 Scenario 30
3.5 Comments 33
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Contents • ix
3.6 Spoken languages 34
3.7 What We Just Learned 35
4. Step Definitions: From the Outside . . . . . . . 39
4.1 Steps and Step Definitions 40
4.2 Capturing Arguments 45
4.3 Multiple Captures 49
4.4 Flexibility 50
4.5 Returning Results 52
4.6 What We Just Learned 58
5. Expressive Scenarios . . . . . . . . . . 61
5.1 Background 61
5.2 Data Tables 64
5.3 Scenario Outline 70
5.4 Nesting Steps 75
5.5 Doc Strings 78
5.6 Staying Organized with Tags and Subfolders 79
5.7 What We Just Learned 82
6. When Cucumbers Go Bad . . . . . . . . . 85
6.1 Feeling the Pain 86
6.2 Working Together 89
6.3 Caring for Your Tests 97
6.4 Stop the Line and Defect Prevention 105
6.5 What We Just Learned 106
Part II — A Worked Example
7. Step Definitions: On the Inside . . . . . . . . 111
7.1 Sketching Out the Domain Model 112
7.2 Removing Duplication with Transforms 117
7.3 Adding Custom Helper Methods to the World 120
7.4 Organizing the Code 128
7.5 What We Just Learned 131
8. Support Code . . . . . . . . . . . . 133
8.1 Fixing the Bug 134
8.2 Bootstrapping the User Interface 141
8.3 Making the Switch 142
8.4 Using Hooks 147
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Contents • x
8.5 Building the User Interface 150
8.6 What We Just Learned 154
9. Dealing with Message Queues and Asynchronous
Components . . . . . . . . . . 157
9.1 Our New Asynchronous Architecture 157
9.2 How to Synchronize 158
9.3 Implementing the New Architecture 161
9.4 Fixing the Flickering Scenario 165
9.5 What We Just Learned 171
10. Databases . . . . . . . . . . . . . 173
10.1 Introducing ActiveRecord 174
10.2 Refactoring to Use a Database 175
10.3 Reading and Writing to the Database 178
10.4 Cleaning the Database with Transactions 181
10.5 Cleaning the Database with Truncation 185
10.6 What We Just Learned 186
Part III — Cucumber Applied
11. The Cucumber Command-Line Interface . . . . . 191
11.1 Cucumber’s Command-Line Options 191
11.2 Running a Subset of Scenarios 192
11.3 Changing Cucumber’s Output 194
11.4 Specifying the Location of Step Definitions 196
11.5 Managing Your Work in Progress (WIP) 197
11.6 Using Profiles 198
11.7 Running Cucumber from Rake 198
11.8 Running Cucumber in Continuous Integration 199
11.9 What We Just Learned 200
12. Testing a REST Web Service . . . . . . . . 201
12.1 In-Process Testing of Rack-Based REST APIs 202
12.2 Out-of-Process Testing of Any REST API 213
12.3 What We Just Learned 220
13. Adding Tests to a Legacy Application . . . . . . 221
13.1 Characterization Tests 222
13.2 Squashing Bugs 224
13.3 Adding New Behavior 225
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