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Java script unit testing

  1. JavaScript Unit Testing 2012 Mats Bryntse @bryntum
  2. var me = { name : ”Mats Bryntse”, age : 35, from : ”Helsingborg, Sweden”, does : ”Runs Bryntum”, site : ””, twitter : ”@bryntum”, likes : ”Ext JS” }; About me
  3. What we do JavaScript scheduling and Gantt charts Siesta (JS Test Tool)
  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)” ”’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
  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 > 4 && userModel.password.length > 8; } }); Mixing view and business logic
  29. Writing testable JS Ext.define('UserModel', { extend: '', name : “”, password : “”, // Returns array of User model objects isValid : function () { return > 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 (
  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
  61. Resources - Yahoo
  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