java script unit testing
DESCRIPTION
My talk at Community Day in Stockholm.TRANSCRIPT
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
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