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)

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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

Pain of Refactoring0

20

40

60

80

100

120

BackendFrontend

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

Sourcepanda = '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 differencesDOM 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”

SeleniumThe most widely used functional testing tool. Firefox

Recorder.

JsTestDriverBy Google. ”Remote JavaScript Console”. IntelliJ and

Eclipse

WatirWeb 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

• JsCoverageSeems abandoned

• ScriptCoverGoogle Chrome Plugin

• JsTestDriverAdd-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 - Yahoohttp://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