JavaScript Unit Testing
2012 Mats Bryntse
@bryntum

var me = {
name : ”Mats Bryntse”,
age : 35,
from : ”Helsingborg, Sweden”,
does : ”Runs Bryntum”,
site : ” www.bryntum.com”,
twitter : ”@bryntum”,
likes : ”Ext JS”
};
About me

What we do
JavaScript scheduling
and Gantt charts
Siesta (JS Test Tool)

</SELFPROMOTION>

First, a quick survey:
How many of you...

• have a web application a frontend test suite?
• have frontend test suite as part of your CI proc.
• run your test suite in all major browsers?
• have zero or less frontend tests for your app.
How many of you...

Unit test JS, really?? But...
”... my code is bug free”
”...testing takes time away from
adding new features (+ new bugs)”
”...it’s QA’s job to test”
”... it’s boring and I’ll quit my job”

Reasons for testing
JavaScript

A typical web app...
Interwebs
http://www.app.com

The backend
• Single controlled platform
• Simple to test and refactor
• Good IDEs and tools
C#
Java
PHP

The frontend
• Multiple platforms & versions
(Mac, Windows XP/Vista/7, Linux...)
• Multiple browser versions
• Hard to refactor
• JavaScript support in IDEs is
still !== awesome

Conclusion
• Developing frontend code is harder than
developing server code.
• Mainly due to lack of good tools
• Lots of uncertainty, x-browser issues
• IE6

As good JS dev tools are hard to find, we need to
make good use of existing tools and practices.

Reasons for testing
JavaScript contd.

Easy to introduce
unforeseen errors
isUserCrazy: function(user, isAdmin) {
// DON’T CHANGE THIS
if (user.age > 35 &&
isAdmin!== true &&
isAdmin!== false) {
user.crazy = true;
}
}

Refactoring is painful
0
20
40
60
80
100
120
Pain of Refactoring
Backend
Frontend

X-browser testing doesn’t
scale
• iOS
• Android
• IE Mobile
• Blackberry
• Firefox mobile
• ...

Efficient debugging
• We spend lots of time debugging frontend
code.
• Helpful to know which parts of an application
is well tested => less likely to have bugs.

Additional benefits of
testing
• Find bugs early
• Develop & refactor with confidence
• Tests serve as additional API documentation
• Helps you detect tightly coupled code

Code handover
• Test cases can be immensely useful when
handing over responsibility for a JS module
• Developer Bob quits his job. New guy gets
responsibility of his JS code.
• How will the new guy know what parts of the
codebase safe to change & refactor?

New guy studies codebase
/* I am not sure if we need this, but too scared to delete. */
// drunk, fix later
// TODO make this work
/**
* When I wrote this, only God and I understood what I was doing
* Now, God only knows
**/
scripts/core/application.js

Code handover
New guy, scared

Code handover
• Without test suite, new guy will be afraid to
make any major changes.
• Only minor cosmetic changes on the surface.
• System accumulates cruft over time.
• Sounds familiar?

So, how do I start..?
• Code and design for testability
• Choose the tools to help you
• Automation / CI / Coverage

Writing testable JS
• Keep your JavaScript in JS files
• Never put JavaScript in your HTML
page/tags
• Keep code organized in logical manageable
files. Decide on some max nbr of lines/file.

Writing testable JS

Writing testable JS
• Fat model, skinny view
• Don’t pollute your views with business logic
• Testing pure JS is a lot easier than testing
DOM-dependent JS
• Promotes reuse of your code

Writing testable JS
Ext.define('UserForm', {
extend: 'Ext.FormPanel',
width: 400,
height: 400,
model: new UserModel(),
// Returns true if User is valid
isValid: function (userModel) {
return userModel.name.length > 4 &&
userModel.password.length > 8;
}
});
Mixing view and business logic

Writing testable JS
Ext.define('UserModel', {
extend: 'Ext.data.Model',
name : “”,
password : “”,
// Returns array of User model objects
isValid : function () {
return this.name.length > 4 &&
this.password.length > 8;
}
});
Better:

Writing testable JS
Ext.define('UserForm', {
extend: 'Ext.FormPanel',
width: 400,
height: 400,
model: new UserModel(),
// Returns true if User is valid
isValid: function (userModel) {
return userModel.isValid();
}
});
No business logic in view

Avoid private code
• Avoid overuse of private functions in
closures
• If your code cannot be accessed it cannot
be tested

Tools

Choose your tools
• Last few years has brought numerous new
testing tools to the JavaScript world
• Quite hard to know which to choose,
evaluation needed
• Positive trend, lots of buzz around web testing

Unit Test Tools
• Jasmine
• Siesta
• Buster.js (beta) / Sinon.js
• DOH (Dojo Object Harness)
• Qunit (jQuery)
• JsUnit (abandoned?)
• YUI Test
• Google js-test
• Zombie (headless/Node)

Pure JS Test Tools
• More or less similar approach in most tools
• Define HTML/JS harness, and test suites is
composed by single JS test files.
• Some support/require setup/tearDown
• Others rely on iframes, slower though no
cleanup required

Jasmine
• Simple DOM-less testing
• BDD syntax
• Borrows “the best parts” of ScrewUnit,
JSSpec, JSpec, and RSpec.

Anatomy of a Jasmine test
describe('panda', function () {
it('is happy', function () {
expect(panda).toBe('happy');
});
});
Suite / Spec
Source
panda = 'happy'; // => PASS

Jasmine matchers

Siesta
• Unit testing and functional DOM testing
• Simple TDD syntax
• Test any JS: Ext JS, jQuery, NodeJS etc.
• Automate using PhantomJS & Selenium.
• Extensible, easy to add own assertion
methods

Anatomy of a Siesta test
StartTest(function(t) {
t.diag('Testing jQuery...');
$('body').html('JQuery was here');
t.contentLike(document.body,
'JQuery was here',
'Found correct text in DOM');
});
test-jquery_01.js

Testing Ajax

Testing Ajax
• Try to avoid calling your actual server.
• Use either static JS files with mock data
(async, slower)
• Or Mock the entire Ajax call (sync, faster)
Sinon.js, Jasmine-ajax etc.

Testing Ajax w/ Jasmine
it("should make an AJAX request to the correct URL", function() {
spyOn($, "ajax");
getProduct(123);
expect($.ajax.mostRecentCall.args[0]["url"]).toEqual("/products/123");
});
function getProduct(id) {
$.ajax({
type: "GET",
url: "/products/" + id,
dataType: "json"
});
}

Functional testing
• Test larger piece of your app, or the
application as a whole.
• Simulate user interaction, click, type etc.
• Navigate between pages

Functional testing tools
• Selenium
• Funcunit
• JsTestDriver
• Siesta
• Watir
• DOH Robot (Dojo)
• Sahi
• Squish (Frog Logic)

Interacting with the DOM
Two main approaches of faking a user
• Synthetic events
• Native events (via Java Applet)

Synthetic events
+ Supported in all major browsers
+ Compatible with mobile
+ Don’t rely on native event queue
Tests can be run in parallell.
- Browsers don’t ”trust” synthetic events
- Enter key on a focused link
- Tab between input fields, etc...
- X-browser differences
DOM Events, Key events, key codes (http://unixpapa.com)

Native events
+ Java applets are supported in all desktop
browsers
+ As close to a ’real’ user as possible
- Won’t work on iOS, Android.
- No parallell tests since native event queue
is used.

”Browser Drivers”
Opens real browser instances and ’drives’
them
Outputs commands and evaluates result
Can be quite slow

”Browser Drivers”
Selenium
The most widely used functional testing tool. Firefox Recorder.
JsTestDriver
By Google. ”Remote JavaScript Console”. IntelliJ and Eclipse
Watir
Web Application Testing in Ruby. Also a .NET port, WatiN.
Sahi
By TytoSoftware. Has X-browser recorder.

Headless browsers
• “A web browser without a graphical user
interface”
• Command line interface
• Great for automating tests, integrating with
CI tools (Jenkins, Cruise Control…)

Headless browsers
+ Run tests on command line
+ Faster
+ Automation
+ Doesn’t require an actual browser
- Not 100% accurate, but close.

Headless browsers
PhantomJS (headless WebKit + JavaScript API)
env.js(Runs on Rhino)
JsDom (CommonJS implementation of the DOM)

Phantom JS
Created by Ariya Hidayat (Sencha Inc.)
Fast headless testing
Site scraping
SVG rendering
Supports CoffeeScript

JS Code Coverage
• JsCoverage
Seems abandoned
• ScriptCover
Google Chrome Plugin
• JsTestDriver
Add-in module for coverage
• JesCov
Rhino, Jasmine

Continuous Integration
• Once you have decided on your testing
toolset, integrate it into your CI.
• Automatically run test suite on pre-commit
or post-commit
• Nightly build, full test suite execution,
reporting via email, or other CI systems.

CI Tools
• Jenkins
• Cruise Control
• Test Swarm

So which tools are
right for me?

Evaluating tools
• Some are geared towards specific server side
languages, Java/Ruby/C#
• Prototype and find what works best for you
• Make sure the tool you use integrates nicely
with your IDE and CI-environment

Resources
http://www.adequatelygood.com/2010/7/Writing-Testable-JavaScript
http://blog.jcoglan.com/2011/07/14/refactoring-towards-testable-javascript-part-1/

Resources - Yahoo
http://screen.yahoo.com/

Resources - GTAC

Finally: wise words
”Without unit tests, you’re not
refactoring. You’re just changing
shit.”
Hamlet D’Arcy

That’s all folks!
Questions?
2012 Mats Bryntse
@bryntum