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WEB APP TESTING USING KNOCKOUT.JS
WEB APP TESTING USING KNOCKOUT.JS

WEB APP TESTING USING KNOCKOUT.JS: Design, implement, and maintain a fully tested JavaScript web application using Knockout.JS

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Profile Icon Roberto Messora
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€18.99 per month
Full star icon Full star icon Full star icon Full star icon Full star icon 5 (3 Ratings)
Paperback Nov 2014 154 pages 1st Edition
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Paperback
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Arrow left icon
Profile Icon Roberto Messora
Arrow right icon
€18.99 per month
Full star icon Full star icon Full star icon Full star icon Full star icon 5 (3 Ratings)
Paperback Nov 2014 154 pages 1st Edition
eBook
€13.98 €19.99
Paperback
€24.99
Subscription
Free Trial
Renews at €18.99p/m
eBook
€13.98 €19.99
Paperback
€24.99
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Free Trial
Renews at €18.99p/m

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WEB APP TESTING USING KNOCKOUT.JS

Chapter 2. The Knockout.JS UI Framework Explained

One of the two main topics of this book is Knockout.JS, a JavaScript library that simplifies the development process of rich and dynamic user interfaces. Knockout.JS is one of many libraries out there that implements a presentation design pattern, in particular the Model-View-ViewModel (MVVM).

We will review Version 3.1 and its most important concepts and features using several examples, and try to understand why this library is so important in relation to testing a web application.

However, this book is not intended to be a complete Knockout.JS compendium; please refer to the Knockout.JS website documentation (http://knockoutjs.com/documentation/introduction.html) to discover all the advanced topics and references that are not covered in this chapter.

In this chapter, you will learn:

  • How to introduce and use Knockout.JS in a web application
  • The data bind mechanism that turns a web application dynamic
  • How Knockout.JS promotes a clear...

Hello Knockout.JS

To start using Knockout.JS is very simple. It is nothing more than a couple of JavaScript lines of code and a special attribute added to the DOM tags.

An example of an HTML page can be as follows:

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>Hello Knockout.JS</title>
</head>
<body>
    <span data-bind="text: message"></span>
    <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/knockout/3.1.0/knockout-min.js"></script>
    <script type="text/JavaScript">
        var viewModel = {
            message: "Hello Knockout.JS!"
        };
        ko.applyBindings(viewModel);
    </script>
</body>
</html>

Note

We put the script tags just before the closing body tag for performance reasons, as stated in the best practices document of the Yahoo Developer Network...

Automatic synchronization between View and ViewModel

In the previous section, we saw a simple example. Now we need to go further to introduce some new concepts. The following example refines the first one:

<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title>Hello Knockout.JS</title>
</head>
<body>
    <span>Type a message:&nbsp;</span>
    <input type="text" data-bind="value: message" />
    <button data-bind="click: submitMessage">Click me</button>
    <script type="text/javascript" src="http://cdnjs.cloudflare.com/ajax/libs/knockout/3.1.0/knockout-min.js"></script>
    <script type="text/JavaScript">
        var ViewModel = function () {
            this.message = ko.observable("");
            this.submitMessage= function () {
                alert(this.message());
      ...

The ViewModel in detail

A ViewModel is a pure-code representation of the View. We saw in the previous sections that it contains data to show and commands that handle events triggered by the user.

It's important to remember that a ViewModel shouldn't have any knowledge about the View and the UI. Pure-code representation means that a ViewModel shouldn't contain any reference to HTML markup elements (buttons, text-boxes, and so on.) but only pure JavaScript properties and methods.

Knockout.JS is a JavaScript implementation of the Model-View-ViewModel presentation design pattern whose objective is to promote a clear separation between the View and ViewModel. This principle is called Separation of Concerns.

Why is this so important? The answer is quite easy, because in this way a developer can achieve a real separation of responsibilities. The View is only responsible for presenting data to the user and reacting to her/his inputs. The ViewModel is also responsible for holding the...

Data-binding in detail

The main objective of a web application is to present some data and eventually react to user inputs. In the previous sections, you learned that the Model-View-ViewModel strategy is to hold the data (the Model) and commands in a pure-code representation of the View called ViewModel. We also briefly scratched the surface of the data-binding mechanism that permits the connection between the ViewModel and HTML markup.

In this section, we will review the Knockout.JS built-in data-binding types. There are many ways to present information on a web page. There are plenty of elements in HTML that need a way to bind the ViewModel properties and commands.

The data-binding syntax

In Knockout.JS, we talk about declarative data-binding because we need to place the data-bind attributes inside the HTML tags, and specify what kind of binding is associated to a ViewModel property/command.

The attribute value must follow a specific syntax in order to allow Knockout.JS to decode its content...

Summary

This chapter is a starting point to learn about how Knockout.JS works. It gives the overall understanding of the Model-View-ViewModel presentation pattern and the most important technical details of this library.

If you look at the big picture, it's easier to see how these techniques foster better web application testing. It's virtually impossible to adequately test a web application without a proper application design. In this respect, you have learned how Knockout.JS promotes a real separation of responsibilities between the View and ViewModel.

In the next chapter, we will dig into a well-known JavaScript unit testing framework. Then, we will put all together to understand how we can take advantage of Knockout.JS in a web application testing strategy.

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Description

If you are a JavaScript developer, beginner, or an expert who wants to improve quality standards in terms of solutions design and functional verification, this book is for you. Basic understanding of web development, HTML, and JavaScript is required.

What you will learn

  • Introduce and use Knockout.JS in a JavaScript web application as a presentation framework
  • Design a JavaScript web application using the wellknown ModelViewViewModel presentation pattern
  • Set up a simple testing environment with Jasmine
  • Unit test a JavaScript web application using the Behavior Driven Development approach
  • Adopt the correct development strategies to obtain the best results in terms of unit testing
  • Install and set up an automated testing environment using Node.JS and Karma
  • Execute unit testing and code coverage on development and minified production code

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Nov 17, 2014
Length: 154 pages
Edition : 1st
Language : English
ISBN-13 : 9781783982844
Vendor :
Netscape
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Product Details

Publication date : Nov 17, 2014
Length: 154 pages
Edition : 1st
Language : English
ISBN-13 : 9781783982844
Vendor :
Netscape
Languages :
Tools :

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Table of Contents

5 Chapters
1. Web Application Testing in the Modern Web Chevron down icon Chevron up icon
2. The Knockout.JS UI Framework Explained Chevron down icon Chevron up icon
3. The Jasmine Unit Testing Framework Explained Chevron down icon Chevron up icon
4. Unit Testing Strategies Chevron down icon Chevron up icon
5. Setting Up an Effective Testing Environment Chevron down icon Chevron up icon

Customer reviews

Rating distribution
Full star icon Full star icon Full star icon Full star icon Full star icon 5
(3 Ratings)
5 star 100%
4 star 0%
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1 star 0%
Scott Addie Dec 13, 2014
Full star icon Full star icon Full star icon Full star icon Full star icon 5
Messora does a fantastic job of reviewing basics of the MVVM development pattern. As a seasoned JavaScript developer who’s used Knockout on a daily basis for a few years and is interested in developing highly testable Single Page Applications (SPAs), this book was of great value. Best practices are clearly identified, and a thorough explanation is provided for each. Ever wondered how to adopt separation of concerns in the JavaScript world to avoid spaghetti code and why it’s a good idea to avoid using jQuery as the cornerstone of your web application? Ever wondered when to choose BDD over TDD to satisfy your testing needs? The answers are found within.Third party libraries such as Jasmine, Gulp, Karma, Phantom, and Postal are introduced. Coming from a Mocha and Grunt background myself, it was worthwhile to see the differences in Jasmine and Gulp, respectively. If you’re just getting started with Jasmine or if you want a refresher course on writing testable JavaScript, consider this book. It’s also a good read for those coming from a jQuery background who are beginning to explore the plethora of MV* frameworks/libraries out there.
Amazon Verified review Amazon
Adam Rackis Dec 15, 2014
Full star icon Full star icon Full star icon Full star icon Full star icon 5
The author does a great job of diving into the MVVM pattern, Knockout.js, as well as a host of technologies and frameworks that can be used to create automated tests for a single page application, including Gulp, postal.js and Jasmine. The writing is crisp and clear, and the book as a whole was a joy to read. Highly recommend.
Amazon Verified review Amazon
Robert Gaut Feb 06, 2015
Full star icon Full star icon Full star icon Full star icon Full star icon 5
I was very pleased to serve as a reviewer on this book. The book is very well-written and is packed with a ton of useful information and practical techniques. The Knockout.JS sections are very clear and approachable to beginners and advanced developers alike. The book especially shines when it comes to unit testing Web apps using Jasmine and the sections on Node.JS, Gulp.JS, Karma, and Phantom.JS are equally impressive. Using the libraries and techniques described in this book have definitely improved my daily development workflows. I highly recommend this book!
Amazon Verified review Amazon
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