Home Programming Jasmine JavaScript Testing

Jasmine JavaScript Testing

By Paulo Vitor Zacharias Ragonha
books-svg-icon Book
eBook $29.99 $20.98
Print $38.99
Subscription $15.99 $10 p/m for three months
$10 p/m for first 3 months. $15.99 p/m after that. Cancel Anytime!
What do you get with a Packt Subscription?
This book & 7000+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with a Packt Subscription?
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with eBook + Subscription?
Download this book in EPUB and PDF formats, plus a monthly download credit
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with a Packt Subscription?
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with eBook?
Download this book in EPUB and PDF formats
Access this title in our online reader
DRM FREE - Read whenever, wherever and however you want
Online reader with customised display settings for better reading experience
What do you get with video?
Download this video in MP4 format
Access this title in our online reader
DRM FREE - Watch whenever, wherever and however you want
Online reader with customised display settings for better learning experience
What do you get with video?
Stream this video
Access this title in our online reader
DRM FREE - Watch whenever, wherever and however you want
Online reader with customised display settings for better learning experience
What do you get with Audiobook?
Download a zip folder consisting of audio files (in MP3 Format) along with supplementary PDF
What do you get with Exam Trainer?
Flashcards, Mock exams, Exam Tips, Practice Questions
Access these resources with our interactive certification platform
Mobile compatible-Practice whenever, wherever, however you want
BUY NOW $10 p/m for first 3 months. $15.99 p/m after that. Cancel Anytime!
eBook $29.99 $20.98
Print $38.99
Subscription $15.99 $10 p/m for three months
What do you get with a Packt Subscription?
This book & 7000+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with a Packt Subscription?
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with eBook + Subscription?
Download this book in EPUB and PDF formats, plus a monthly download credit
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with a Packt Subscription?
This book & 6500+ ebooks & video courses on 1000+ technologies
60+ curated reading lists for various learning paths
50+ new titles added every month on new and emerging tech
Early Access to eBooks as they are being written
Personalised content suggestions
Customised display settings for better reading experience
50+ new titles added every month on new and emerging tech
Playlists, Notes and Bookmarks to easily manage your learning
Mobile App with offline access
What do you get with eBook?
Download this book in EPUB and PDF formats
Access this title in our online reader
DRM FREE - Read whenever, wherever and however you want
Online reader with customised display settings for better reading experience
What do you get with video?
Download this video in MP4 format
Access this title in our online reader
DRM FREE - Watch whenever, wherever and however you want
Online reader with customised display settings for better learning experience
What do you get with video?
Stream this video
Access this title in our online reader
DRM FREE - Watch whenever, wherever and however you want
Online reader with customised display settings for better learning experience
What do you get with Audiobook?
Download a zip folder consisting of audio files (in MP3 Format) along with supplementary PDF
What do you get with Exam Trainer?
Flashcards, Mock exams, Exam Tips, Practice Questions
Access these resources with our interactive certification platform
Mobile compatible-Practice whenever, wherever, however you want
About this book
Publication date:
April 2015
Publisher
Packt
Pages
134
ISBN
9781785282041

 

Chapter 1. Getting Started with Jasmine

It is an exciting time to be a JavaScript developer; technologies have matured, web browsers are more standardized, and there are new things to play with every day. JavaScript has become an established language, and the Web is the true open platform of today. We've seen the rise of single-page web applications, the proliferation of Model View Controller (MVC) frameworks, such as Backbone.js and AngularJS, the use of JavaScript on the server with Node.js, and even mobile applications created entirely with HTML, JavaScript, and CSS using technologies such as PhoneGap.

From its humble beginnings with handling HTML forms, to the massive applications of today, the JavaScript language has come very far, and with it, a number of tools have matured to ensure that you can have the same level of quality with it that you have with any other language.

This book is about the tools that keep you in control of your JavaScript development.

 

JavaScript – the bad parts


There are many complications when dealing with client JavaScript code; the obvious one, is that you cannot control the client's runtime. While on the server, you can run a specific version of your Node.js server, you can't oblige your clients to run the latest version of Chrome or Firefox.

The JavaScript language is defined by the ECMAScript specification; therefore, each browser can have its own implementation of a runtime, which means there could be small differences or bugs between them.

Besides that, you have issues with the language itself. Brendan Eich developed JavaScript in just 10 days, under a lot of management pressure at Netscape. Although it got itself right in its simplicity, first-class functions, and object prototypes, it also introduced some problems with the attempt to make the language malleable and allow it to evolve.

Every JavaScript object is mutable; this means that there is nothing you can do to prevent a module from overwriting pieces of other modules. The following code illustrates how simple it is to overwrite the global console.log function:

console.log('test');
>> 'test'
console.log = 'break';
console.log('test');
>> TypeError: Property 'log' of object #<Console> is not a function

This was a conscious decision on the language design; it allows developers to tinker and add missing functionality to the language. But given such power, it is relatively easy to make a mistake.

Version 5 of the ECMA specification introduced the Object.seal function, which prevents further changes on any object once called. But its current support is not widespread; Internet Explorer, for example, only implemented it on its version 9.

Another problem, is with how JavaScript deals with type. In other languages, an expression like '1' + 1 would probably raise an error; in JavaScript, due to some non-intuitive type coercion rules, the aforementioned code results in '11'. But the main problem is in its inconsistency; on multiplication, a string is converted into a number, so '3' * 4, is actually 12.

This can lead to some hard-to-find problems on big expressions. Suppose you have some data coming from a server, and although you are expecting numbers, one value came as a string:

var a = 1, b = '2', c = 3, d = 4;
var result = a + b + c * d;

The resulting value of the preceding example is '1212', a string.

These are just two common problems faced by developers. Throughout the book, you are going to apply best practices and write tests to guarantee that you don't fall into these, and other, pitfalls.

 

Jasmine and behavior-driven development


Jasmine is a little behavior-driven development (BDD) test framework created by the developers at Pivotal Labs, to allow you to write automated JavaScript unit tests.

But before we can go any further, first we need to get some fundamentals right, starting with what a test unit is.

A test unit is a piece of code that tests a functionality unit of the application code. But sometimes, it can be tricky to understand what a functionality unit can be, so for that reason, Dan North came up with a solution in the form of BDD, which is a rethink of test-driven development (TDD).

In traditional unit testing practice, the developer is left with loose guidelines on how to start the process of testing, what to test, how big a test should be, or even how to call a test.

To fix these problems, Dan took the concept of user stories from the standard agile construct, as a model on how to write tests.

For example, a music player application could have an acceptance criterion such as:

Given a player, when the song has been paused, then it should indicate that the song is currently paused.

As shown in the following list, this acceptance criterion is written following an underlying pattern:

  • Given: This provides an initial context

  • When: This defines the event that occurs

  • Then: This ensures an outcome

In Jasmine, this translates into a very expressive language that allows tests to be written in a way that reflects actual business values. The preceding acceptance criterion written as a Jasmine test unit would be as follows:

describe("Player", function() {
  describe("when song has been paused", function() {
    it("should indicate that the song is paused", function() {

    });
  });
});

You can see how the criterion translates well into the Jasmine syntax. In the next chapter, we will get into the details of how these functions work.

With Jasmine, as with other BDD frameworks, each acceptance criterion directly translates to a test unit. For that reason, each test unit is usually called a spec, short for specification. During the course of this book, we will be using this terminology.

 

Downloading Jasmine


Getting started with Jasmine is actually pretty simple.

Open the Jasmine website at http://jasmine.github.io/2.1/introduction.html#section-Downloads and download the Standalone Release (version 2.1.3 is going to be used in the book).

While at the Jasmine website, you might notice that it is actually a live page executing the specs contained in it. This is made possible by the simplicity of the Jasmine framework, allowing it to be executed in the most diverse environments.

After you've downloaded the distribution and uncompressed it, you can open the SpecRunner.html file on your browser. It will show the results of a sample test suite (including the acceptance criterion we showed you earlier):

This shows the SpecRunner.html file opened on the browser

This SpecRunner.html file is a Jasmine browser spec runner. It is a simple HTML file that references the Jasmine code, the source files, and the test files. For convention purposes, we are going to refer to this file simply as runner.

You can see how simple it is by opening it on a text editor. It is a small HTML file that references the Jasmine source:

<script src="lib/jasmine-2.1.3/jasmine.js"></script>
<script src="lib/jasmine-2.1.3/jasmine-html.js"></script>
<script src="lib/jasmine-2.1.3/boot.js"></script>

The runner references the source files:

<script type="text/javascript" src="src/Player.js"></script>
<script type="text/javascript" src="src/Song.js"></script>

The runner references a special SpecHelper.js file that contains code shared between specs:

<script type="text/javascript" src="spec/SpecHelper.js"></script>

The runner also references the spec files:

<script type="text/javascript" src="spec/PlayerSpec.js"></script>

Tip

Downloading the example code

You can download the example code files for all Packt books you have purchased from your account at http://www.packtpub.com. If you purchased this book elsewhere, you can visit http://www.packtpub.com/support and register to have the files e-mailed directly to you.

The Jasmine framework is set up inside the lib/jasmine-2.1.3/boot.js file, and although it's an extensive file, most of its content is in documentation on how the setup actually happens. It is recommended that you open it in a text editor and study its content.

Although, for now, we are running the specs in the browser, in Chapter 8, Build Automation, we are going to make the same specs and code run on a headless browser, such as PhantomJS, and have the results written on the console.

A headless browser is a browser environment without its graphical user interface. It can either be an actual browser environment, such as PhantomJS, which uses the WebKit rendering engine, or a simulated browser environment, such as Envjs.

And although not covered in this book, Jasmine can also be used to test server-side JavaScript code written for environments such as Node.js.

This Jasmine flexibility is amazing, because you can use the same tool to test all sorts of JavaScript code.

 

Summary


In this chapter, you saw some of the motivations behind testing a JavaScript application. I showed you some common pitfalls of the JavaScript language and how BDD and Jasmine both help you to write better tests.

You have also seen how easy it is to download and get started with Jasmine.

In the next chapter, you are going to learn how to think in BDD and code your very first spec.

About the Author
  • Paulo Vitor Zacharias Ragonha

    Paulo Ragonha is a software engineer with over 7 years of professional experience. An advocate of the open Web, he is inspired and driven to build compelling experiences on top of this ubiquitous platform. H e loves to hack, so you will often see him wandering around in conferences or attending hackathons. His most recent professional experiences ranged from DevOps (with Chef and Docker) to moving up the stack with Node.js, Ruby, and Python and all the way toward building single-page applications (mostly with Backbone.js and "ad hoc" solutions). Passionate about automation, he sees testing as a liberating tool to enjoy the craft of writing code even more. Back in 2013, he wrote the first edition of the book Jasmine JavaScript Testing, Packt Publishing. Paulo has an amazing wife, who he loves very much. He lives in beautiful Florianópolis, a coastal city in the south of Brazil. He is a casual speaker, a biker, a runner, and a hobbyist photographer.

    Browse publications by this author
Jasmine JavaScript Testing
Unlock this book and the full library FREE for 7 days
Start now