understanding javascript testing
DESCRIPTION
A talk given at the Boston Developer Day and at the 2009 jQuery Conference.TRANSCRIPT
JavaScript TestingJohn 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.
What should I use?
Looong Tail
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Other
People don’t test. :-(
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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" ); });
QUnit
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() { var result = new top.jsUnitTestSuite(); result.addTestPage("tests/server/jsUnitVersionCheckTests.html"); result.addTestPage("tests/server/jsUnitServerAjaxTests.html"); return result; }
function librariesSuite() { var result = new top.jsUnitTestSuite(); 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); }
JSUnit
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 2
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); } });
YUITest 3
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"]); }); }); });
Screw.Unit
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:'[email protected]', 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"); } })
JSSpec
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/
Selenium 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)
Browser Launching
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.jarRhino 1.6 release 6 2007 06 28js> 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/
TestSwarm
Choose Your Browsers
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 GridIE 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 GridIE 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
TestSwarm
FF 3
FF 3
FF 3.5 FF 3.5 FF 3.5IE 6
IE 6
IE 6
IE 7
IE 7
Op 9
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/