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Java script unit testing

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My talk at Community Day in Stockholm.

My talk at Community Day in Stockholm.

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  • 1. JavaScript Unit Testing 2012 Mats Bryntse @bryntum
  • 2. var me = { name : ”Mats Bryntse”, age : 35, from : ”Helsingborg, Sweden”, does : ”Runs Bryntum”, site : ” www.bryntum.com”, twitter : ”@bryntum”, likes : ”Ext JS” }; About me
  • 3. What we do JavaScript scheduling and Gantt charts Siesta (JS Test Tool)
  • 4. </SELFPROMOTION>
  • 5. First, a quick survey: How many of you...
  • 6. • 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...
  • 7. 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”
  • 8. Reasons for testing JavaScript
  • 9. A typical web app... Interwebs http://www.app.com
  • 10. The backend • Single controlled platform • Simple to test and refactor • Good IDEs and tools C# Java PHP
  • 11. The frontend • Multiple platforms & versions (Mac, Windows XP/Vista/7, Linux...) • Multiple browser versions • Hard to refactor • JavaScript support in IDEs is still !== awesome
  • 12. Conclusion • Developing frontend code is harder than developing server code. • Mainly due to lack of good tools • Lots of uncertainty, x-browser issues • IE6
  • 13. As good JS dev tools are hard to find, we need to make good use of existing tools and practices.
  • 14. Reasons for testing JavaScript contd.
  • 15. Easy to introduce unforeseen errors isUserCrazy: function(user, isAdmin) { // DON’T CHANGE THIS if (user.age > 35 && isAdmin!== true && isAdmin!== false) { user.crazy = true; } }
  • 16. Refactoring is painful 0 20 40 60 80 100 120 Pain of Refactoring Backend Frontend
  • 17. X-browser testing doesn’t scale • iOS • Android • IE Mobile • Blackberry • Firefox mobile • ...
  • 18. 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.
  • 19. Additional benefits of testing • Find bugs early • Develop & refactor with confidence • Tests serve as additional API documentation • Helps you detect tightly coupled code
  • 20. 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?
  • 21. 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
  • 22. Code handover New guy, scared
  • 23. 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?
  • 24. So, how do I start..? • Code and design for testability • Choose the tools to help you • Automation / CI / Coverage
  • 25. 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.
  • 26. Writing testable JS
  • 27. 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
  • 28. 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
  • 29. 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:
  • 30. 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
  • 31. Avoid private code • Avoid overuse of private functions in closures • If your code cannot be accessed it cannot be tested
  • 32. Tools
  • 33. 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
  • 34. 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)
  • 35. 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
  • 36. Jasmine • Simple DOM-less testing • BDD syntax • Borrows “the best parts” of ScrewUnit, JSSpec, JSpec, and RSpec.
  • 37. Anatomy of a Jasmine test describe('panda', function () { it('is happy', function () { expect(panda).toBe('happy'); }); }); Suite / Spec Source panda = 'happy'; // => PASS
  • 38. Jasmine matchers
  • 39. 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
  • 40. Anatomy of a Siesta test StartTest(function(t) { t.diag('Testing jQuery...'); $('body').html('JQuery was here'); t.contentLike(document.body, 'JQuery was here', 'Found correct text in DOM'); }); test-jquery_01.js
  • 41. Testing Ajax
  • 42. Testing Ajax • Try to avoid calling your actual server. • Use either static JS files with mock data (async, slower) • Or Mock the entire Ajax call (sync, faster) Sinon.js, Jasmine-ajax etc.
  • 43. Testing Ajax w/ Jasmine it("should make an AJAX request to the correct URL", function() { spyOn($, "ajax"); getProduct(123); expect($.ajax.mostRecentCall.args[0]["url"]).toEqual("/products/123"); }); function getProduct(id) { $.ajax({ type: "GET", url: "/products/" + id, dataType: "json" }); }
  • 44. Functional testing • Test larger piece of your app, or the application as a whole. • Simulate user interaction, click, type etc. • Navigate between pages
  • 45. Functional testing tools • Selenium • Funcunit • JsTestDriver • Siesta • Watir • DOH Robot (Dojo) • Sahi • Squish (Frog Logic)
  • 46. Interacting with the DOM Two main approaches of faking a user • Synthetic events • Native events (via Java Applet)
  • 47. 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)
  • 48. 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.
  • 49. ”Browser Drivers” Opens real browser instances and ’drives’ them Outputs commands and evaluates result Can be quite slow
  • 50. ”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.
  • 51. Headless browsers • “A web browser without a graphical user interface” • Command line interface • Great for automating tests, integrating with CI tools (Jenkins, Cruise Control…)
  • 52. Headless browsers + Run tests on command line + Faster + Automation + Doesn’t require an actual browser - Not 100% accurate, but close.
  • 53. Headless browsers PhantomJS (headless WebKit + JavaScript API) env.js(Runs on Rhino) JsDom (CommonJS implementation of the DOM)
  • 54. Phantom JS Created by Ariya Hidayat (Sencha Inc.) Fast headless testing Site scraping SVG rendering Supports CoffeeScript
  • 55. JS Code Coverage • JsCoverage Seems abandoned • ScriptCover Google Chrome Plugin • JsTestDriver Add-in module for coverage • JesCov Rhino, Jasmine
  • 56. 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.
  • 57. CI Tools • Jenkins • Cruise Control • Test Swarm
  • 58. So which tools are right for me?
  • 59. 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
  • 60. Resources http://www.adequatelygood.com/2010/7/Writing-Testable-JavaScript http://blog.jcoglan.com/2011/07/14/refactoring-towards-testable-javascript-part-1/
  • 61. Resources - Yahoo http://screen.yahoo.com/
  • 62. Resources - GTAC
  • 63. Finally: wise words ”Without unit tests, you’re not refactoring. You’re just changing shit.” Hamlet D’Arcy
  • 64. That’s all folks! Questions? 2012 Mats Bryntse @bryntum

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