Test-Driving JavaScript Applications: Rapid, Confident, Maintainable Code

357 Pages·2016·10.21 MB·English

by  Venkat Subramaniam

Early praise for Test-Driving JavaScript Applications
Not only does this book provide step-by-step instructions for how to test JavaScript,
Venkat also presents a simplified, well-rounded approach to driving out good de-
sign. Venkat writes with a compelling and humorous voice that makes the content
educational and entertaining.
➤ Kimberly D. Barnes
Senior software engineer, GoSpotCheck
Venkat has, in his usual inimitable style, taken the swamp of JavaScript testing
and drained it into a clear pool. He has taken a welcome pragmatic approach to
the subject of testing this sometimes tricky platform, providing frameworks, tools,
and valuable tips and insights along the way. Highly recommended.
➤ Neal Ford
Director/software architect/meme wrangler, Thoughtworks, Inc.
If you are a seasoned TDD practitioner in another language, this book answers
all the questions to test-drive JavaScript applications. If you are a JavaScript
programmer who hasn’t yet embraced TDD, Venkat takes you through several
real-world examples to get you started with confidence.
➤ Naresha K.
Chief technologist, Channel Bridge Software Labs
Test-Driving JavaScript Applications has shown me how to use TDD for the front
end. This book was exactly what I was looking for. It has practical examples and
lots of useful information. I’ve learned good practices, and I’ve stopped writing
legacy code.
➤ Astefanoaie Nicolae Stelian
Senior programmer, PRISA
Test-Driving JavaScript Applications
Rapid, Confident, Maintainable Code
Venkat Subramaniam
The Pragmatic Bookshelf
Raleigh, North Carolina
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ISBN-13: 978-1-68050-174-2
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Book version: P1.0—October 2016
In loving memory of professor and uncle PSK,
for lighting my passion for programming.

Contents
Acknowledgments . . . . . . . . . . . xi
Introduction . . . . . . . . . . . . xiii
1. Automation Shall Set You Free . . . . . . . . 1
The Challenges of Change 1
Testing vs. Verification 2
Adopting Automated Verification 3
Why Is It Hard to Verify? 6
How to Approach Automated Testing 7
Wrapping Up 8
Part I — Creating Automated Tests
2. Test-Drive Your Design . . . . . . . . . . 11
Let’s Get Started 12
Design with Positive, Negative, and Exception Tests 21
Design Server-Side Code 23
Measure Server-Side Code Coverage 33
Prepare for Client-Side Testing 36
Design Client-Side Code 40
Measure Client-Side Code Coverage 43
Wrapping Up 44
3. Test Asynchrony . . . . . . . . . . . 45
Server-Side Callbacks 46
Client-Side Callbacks 51
Test Your Promises 54
Wrapping Up 60
Contents • viii
4. Tactfully Tackle Dependencies . . . . . . . . 61
A Problem and Spiking to Learn 61
Visualize a Modular Design 64
Separate Dependencies Where Possible 65
Employ Test Doubles 68
Inject the Dependencies 71
Test Interactions 72
Use Sinon to Reduce Noise 75
Review and Run 84
Wrapping Up 88
Part II — Real-World Automated Testing
5. Test-Drive Node.js Apps . . . . . . . . . . 91
Start with a Strategic—Just Enough—Design 91
Leap Into Tactical—Test First—Design 93
Continue the Design 99
Create a Spike to Gain Insight 102
Modularize to Facilitate Testing 108
Separate Concerns 112
Integrate and Run 114
Review the Coverage and Design 117
Providing HTTP Access 119
Wrapping Up 120
6. Test-Drive Express Apps . . . . . . . . . 121
Design for Testability 121
Set Up the Express App and Run a Canary Test 124
Design the Database Connection 125
Design the Model 129
Design the Routes 144
Measure Code Coverage 154
Take It for a Drive 156
Wrapping Up 160
7. Working with the DOM and jQuery . . . . . . . 161
Create a Strategic Design 161
Create the Tactical Design with Tests 162
Evolve Code in Small Steps 164
Take the UI for a Short Drive 175