Understanding JavaScript Testing

JavaScript Testing
John Resig
http://ejohn.org/ - http://twitter.com/jeresig

Why Test JavaScript?
✦ Cross-browser issues.
✦ The possibility for causing an unforeseen
problem is simply too great.

Looong Tail

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0

Other

People don’t test. :-(

900

675

450

225

0

None

Basic Components
✦ Writing and understanding a JavaScript
test suite is easy.
✦ Test Suite
✦ Tests
✦ Assertions
✦ Async Tests

✦ Test Runner

Assertions
<html>
<head>
   <title>Test Suite</title>
   <script>
   function assert( value, desc ) {
     var li = document.createElement("li");
     li.className = value ? "pass" : "fail";
     li.appendChild( document.createTextNode( desc ) );
     document.getElementById("results").appendChild( li );
   }

   window.onload = function(){
     assert( true, "The test suite is running." );
   };
   </script>
   <style>
     #results li.pass { color: green; }
     #results li.fail { color: red; }
   </style>
</head>
<body>
   <ul id="results"></ul>
</body>
</html>

Tests
     test("A test.", function(){
       assert( true, "First assertion completed" );
       assert( true, "Second assertion completed" );
       assert( true, "Third assertion completed" );
     });

     test("Another test.", function(){
       assert( true, "First test completed" );
       assert( false, "Second test failed" );
       assert( true, "Third assertion completed" );
     });

Tests
   var results;

   function assert( value, desc ) {
     var li = document.createElement("li");
     li.className = value ? "pass" : "fail";
     li.appendChild( document.createTextNode( desc ) );
     results.appendChild( li );
     if ( !value ) {
       li.parentNode.parentNode.className = "fail";
     }
     return li;
   }

   function test(name, fn){
     results = document.getElementById("results");
     results = assert( true, name ).appendChild(
       document.createElement("ul") );
     fn();
   }

Async Tests
test(function(){
   pause();
   setTimeout(function(){
     assert( true, "First test completed" );
     resume();
   }, 100);
});

test(function(){
   pause();
   setTimeout(function(){
     assert( true, "Second test completed" );
     resume();
   }, 200);
});

Async Tests
(function(){
   var queue = [], paused = false;

   this.test = function(fn){
     queue.push( fn );
     runTest();
   };

   this.pause = function(){
     paused = true;
   };

   this.resume = function(){
     paused = false;
     setTimeout(runTest, 1);
   };

   function runTest(){
     if ( !paused && queue.length ) {
       queue.shift()();
       if ( !paused ) {
         resume();
       }
     }
   }
})();

TestRunner
✦ Responsible for loading an executing tests.
✦ Sometimes individual test groups can run
standalone (Dojo) sometimes they require
the test runner (QUnit, JSUnit).

Popular Test Frameworks

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QUnit JSUnit Selenium YUITest FireUnit Screw.Unit JSSpec

Unit Testing
✦ Break code into logical chucks for testing.
✦ Focus on one method at a time.
✦ Popular Frameworks:
✦ QUnit
✦ JSUnit
✦ YUITest

QUnit
✦ Unit Testing framework built for jQuery.
✦ Additional features:
✦ Supports asynchronous testing.
✦ Can break code into modules.
✦ Supports test timeouts.

✦ http://docs.jquery.com/QUnit

QUnit Style
test("a basic test example", function() {
   ok( true, "this test is fine" );
   var value = "hello";
   equals( "hello", value, "We expect value to be hello" );
});

module("Module A");

test("first test within module", function() {
   ok( true, "all pass" );
});

test("second test within module", function() {
   ok( true, "all pass" );
});

module("Module B");

test("some other test", function() {
   expect(2);
   equals( true, false, "failing test" );
   equals( true, true, "passing test" );
});

JSUnit
✦ One of the oldest JavaScript testing
frameworks.
✦ A port of JUnit to JavaScript, circa 2001.
✦ Code feels very 2001 (frames!)
✦ http://www.jsunit.net/

JSUnit
       function coreSuite() {
           var result = new top.jsUnitTestSuite();
           result.addTestPage("tests/jsUnitAssertionTests.html");
           result.addTestPage("tests/jsUnitSetUpTearDownTests.html");
           result.addTestPage("tests/jsUnitRestoredHTMLDivTests.html");
           result.addTestPage("tests/jsUnitFrameworkUtilityTests.html");
           result.addTestPage("tests/jsUnitOnLoadTests.html");
           result.addTestPage("tests/jsUnitUtilityTests.html");
           return result;
       }

       function serverSuite() {
           result.addTestPage("tests/server/jsUnitVersionCheckTests.html");
           result.addTestPage("tests/server/jsUnitServerAjaxTests.html");
           return result;
       }

       function librariesSuite() {
           result.addTestPage("tests/jsUnitMockTimeoutTest.html");
           return result;
       }

       function suite() {
           var newsuite = new top.jsUnitTestSuite();
           newsuite.addTestSuite(coreSuite());
           newsuite.addTestSuite(serverSuite());
           newsuite.addTestSuite(librariesSuite());
           return newsuite;
       }

JSUnit
function testAssertNotUndefined() {
     assertNotUndefined("1 should not be undefined", 1);
     assertNotUndefined(1);
}

function testAssertNaN() {
     assertNaN("a string should not be a number", "string");
     assertNaN("string");
}

function testAssertNotNaN() {
     assertNotNaN("1 should not be not a number", 1);
     assertNotNaN(1);
}

function testFail() {
     var excep = null;
     try {
         fail("Failure message");
     } catch (e) {
         excep = e;
     }
     assertJsUnitException("fail(string) should throw a JsUnitException", excep);
}

function testTooFewArguments() {
     var excep = null;
     try {
         assert();
     } catch (e1) {
         excep = e1;
     }
     assertNonJsUnitException("Calling an assertion function with too
few arguments should throw an exception", excep);
}

YUITest (2 & 3)
✦ Testing framework built and developed by
Yahoo (released Oct 2008).
✦ Completely overhauled to go with YUI v3.
✦ Features:
✦ Supports async tests.
✦ Has good event simulation.

✦ v2: http://developer.yahoo.com/yui/
examples/yuitest/
✦ v3: http://developer.yahoo.com/yui/3/test/

YUITest 2
  YAHOO.example.yuitest.ArrayTestCase = new YAHOO.tool.TestCase({
     name : "Array Tests",

     setUp : function () {
         this.data = [0,1,2,3,4]
     },

     tearDown : function () {
         delete this.data;
     },

     testPop : function () {
         var Assert = YAHOO.util.Assert;
         var value = this.data.pop();

         Assert.areEqual(4, this.data.length);
         Assert.areEqual(4, value);
     },

     testPush : function () {
         var Assert = YAHOO.util.Assert;

         this.data.push(5);

         Assert.areEqual(6, this.data.length);
         Assert.areEqual(5, this.data[5]);
     }
});

YUITest 3
Y.example.test.DataTestCase = new Y.Test.Case({
     name : "Data Tests",

     setUp : function () {
         this.data = {
             name: "test",
             year: 2007,
             beta: true
         };
     },

     tearDown : function () {
         delete this.data;
     },

     testName : function () {
         var Assert = Y.Assert;

         Assert.isObject(this.data);
         Assert.isString(this.data.name);
         Assert.areEqual("test", this.data.name);
     },

     testYear : function () {
         var Assert = Y.Assert;

         Assert.isObject(this.data);
         Assert.isNumber(this.data.year);
         Assert.areEqual(2007, this.data.year);
     }
});

Behavior Testing
✦ Similar to unit testing, but broken up by
task.
✦ Functionally very similar to unit testing,
uses diﬀerent terminology
✦ Popular frameworks:
✦ Screw.Unit
✦ JSSpec

Screw.Unit
✦ Popular BDD framework.
✦ http://github.com/nathansobo/screw-unit/
tree/master

Screw.Unit
describe("a nested describe", function() {
   var invocations = [];

   before(function() {
     invocations.push("before");
   });

   describe("a doubly nested describe", function() {
     before(function() {
       invocations.push('inner before');
     });

     it("runs befores in all ancestors prior to an it", function() {
       expect(invocations).to(equal, ["before", "inner before"]);
     });
   });
});

JSSpec
✦ Used by MooTools as their testing
framework.
✦ http://jania.pe.kr/aw/moin.cgi/JSSpec

JSSpec
describe('"Should have"s', {
   'String length': function() {
     expect("Hello").should_have(4, "characters");
   },
   'Array length': function() {
     expect([1,2,3]).should_have(4, "items");
   },
   'Object's item length': function() {
     expect({name:'Alan Kang', email:'jania902@gmail.com',
accounts:['A', 'B']}).should_have(3, "accounts");
   },
   'No match': function() {
     expect("This is a string").should_have(5, "players");
   },
   'Exactly': function() {
     expect([1,2,3]).should_have_exactly(2, "items");
   },
   'At least': function() {
     expect([1,2,3]).should_have_at_least(4, "items");
   },
   'At most': function() {
     expect([1,2,3]).should_have_at_most(2, "items");
   }
})

Automation
✦ Functional Testing
✦ Browser launching
✦ Server-Side

Functional Testing
✦ Selenium IDE
✦ There may be others by Selenium is far
and away the best.

Selenium IDE
✦ Records and automates actions performed
by a user.
✦ An extension for Firefox that records the
actions.
✦ Can play them back in all browsers
(limited by cross-domain issues).
✦ Primarily for testing web applications -
everyone should use it, though!
✦ http://seleniumhq.org/projects/ide/

Browser Launching
✦ Automates the process of opening browser
windows, running tests, and getting results.
✦ Frequently require a speciﬁc framework.
✦ Popular frameworks:
✦ WebDriver http://code.google.com/p/
webdriver/ (Java)
✦ Waitr http://wtr.rubyforge.org/ (Ruby)
✦ JsTestDriver http://code.google.com/p/
js-test-driver/ (Java)
✦ Selenium RC http://seleniumhq.org/
projects/remote-control/ (Java)

Server-Side
✦ Ignore the browser! Simulate it on the
server-side.
✦ Almost always uses Java + Rhino to
construct a browser.
✦ Some frameworks:
✦ Crosscheck
✦ Env.js
✦ Blueridge

Server-Side
✦ Crosscheck
✦ Pure Java, even simulates browser bugs.
✦ http://www.thefrontside.net/crosscheck

✦ Env.js
✦ Pure JavaScript, focuses on standards
support.
✦ http://github.com/thatcher/env-js/tree/
master
✦ Blueridge
✦ Env.js + Screw.Unit + Rhino
✦ http://github.com/relevance/blue-ridge/

Env.js
$ java -jar build/js.jar
Rhino 1.6 release 6 2007 06 28
js> load('build/runtest/env.js');

js> window.location = 'test/index.html';
test/index.html

js> load('dist/jquery.js');

// Add pretty printing to jQuery objects:
js> jQuery.fn.toString = DOMNodeList.prototype.toString;

js> $('span').remove();
[ <span#å°åŒ—Taibei>, <span#å°åŒ—>, <span#utf8class1>,
<span#utf8class2>, <span#foo:bar>, <span#test.foo[5]bar> ]

// Yes - UTF-8 is supported in DOM documents!
js> $('span')
[ ]

js> $('div').append('<span><b>hello!</b> world</span>');
[ <div#main>, <div#foo> ]

js> $('span')
[ <span>, <span> ]

js> $('span').text()
hello! worldhello! world

Distributed
✦ Selenium Grid
✦ Push Selenium tests out to many
machines (that you manage),
simultaneously.
✦ Collect and store the results.
✦ http://selenium-grid.seleniumhq.org/

✦ TestSwarm
✦ Push tests to a distributed swarm of
clients.
✦ Results viewable on the server.
✦ http://testswarm.com/

Cost / Beneﬁt

IE 7 IE 6 FF 3 Safari 3 Opera 9.5
Cost Benefit

Draw a line in the sand.

Graded Support

Yahoo Browser Compatibility

Browser Support Grid
IE Firefox Safari Opera Chrome

Previous 6.0 2.0 3.0 9.5

Current 7.0 3.0 3.2 9.6 1.0

Next 8.0 3.1 4.0 10.0 2.0

jQuery Browser Support

Browser Support Grid
IE Firefox Safari Opera Chrome

Previous 6.0 2.0 3.0 9.5

Current 7.0 3.0 3.2 9.6 1.0

Next 8.0 3.1 4.0 10.0 2.0

jQuery 1.3 Browser Support

The Scaling Problem
✦ The Problem:
✦ jQuery has 6 test suites
✦ Run in 11 browsers
✦ (Not even including multiple platforms!)

✦ All need to be run for every commit,
patch, and plugin.
✦ JavaScript testing doesn’t scale well.

Distributed Testing
✦ Hub server
✦ Clients connect and help run tests
✦ A simple JavaScript client that can be run
in all browsers
✦ Including mobile browsers!

✦ TestSwarm

FF 3.5 FF 3.5 FF 3.5
IE 6
IE 6
FF 3 IE 6
Op 9
FF 3

IE 7

TestSwarm
IE 7

Test Suite Test Suite Test Suite

Manual Testing
✦ Push tests to users who follow pre-deﬁned
steps
✦ Answer ‘Yes’/’No’ questions which are
pushed back to the server.
✦ An eﬀective way to distribute manual test
load to dozens of clients.

TestSwarm.com
✦ Incentives for top testers (t-shirts, books)
✦ Will be opening for alpha testing very soon
✦ Help your favorite JavaScript library
become better tested!
✦ http://testswarm.com

Questions
✦ Contact:
✦ John Resig
✦ http://ejohn.org/
✦ http://twitter.com/jeresig

✦ More info:
✦ http://jsninja.com/Overview
✦ http://ejohn.org/blog/javascript-testing-
does-not-scale/

Understanding JavaScript Testing

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