This chapter covers

• Why testing is important
• What unit testing means
• Installing QUnit
• Testing your JavaScript code with QUnit
• How to create a complete test suite with QUnit

14.1 Why is testing important

14.1.1 Why unit testing

• Attest that the code returns expected results given specific inputs.
• Discover the highest number of defects in an early stage (related to the previous point).
• Improve the design of the code.
• Identify units that are too complex.

14.1.2 Frameworks for unit testing

JavaScript
QUnit
Mocha
Jasmine (behavior-driven development)

14.2 Getting started with QUnit

14.3 Creating tests for synchronous code

QUnit.test(name, test)
Parameters
name (String)
test (Function)
Returns
undefined

QUnit.test('My first test', function(assert) {
  //Code here...
});

expect(total)
Parameters
total (Number)
Returns
undefined

QUnit.test('My first test', function(assert){
  assert.expect(0);
});

14.4 Testing your code using assertions

14.4.1 equal(), strictEqual(), notEqual(), and notStrictEqual()

equal(value, expected[, message])
Parameters
value (Any)
expected (Any)
message (String)
Returns
undefined

function sum(a, b) {
return a + b;
}

QUnit.test('My first test', function(assert) {
 assert.expect(3);
 assert.equal(sum(2, 2), 4, 'Sum of two positive numbers');
 assert.equal(sum(-2, -2), -4, 'Sum of two negative numbers');
 assert.equal(sum(2, 0), 2, 'Sum of a positive number and the neutral
element');
});

strictEqual(value, expected[, message])
Parameters
value (Any)
expected (Any)
message (String)
Returns
undefined

assert.equal($.trim(' '), '',
 'Trimming a spaces-only string returns an empty string');
assert.strictEqual($('input:checked').length,
 $('input').filter(':checked').length,
 'Filtering elements in advance or later produce the same number of
 elements');
assert.notEqual($('input:checked'), $('input').filter(':checked'),
 'Two jQuery objects are different unless they point to the same memory
 address');
assert.notStrictEqual(new Array(1, 2, 3), [1, 2, 3],
 'Two arrays are different unless they point to the same memory address');

14.4.2 The other assertion methods

An overview of other assertion methods provided by QUnit

function isEven(number) {
  return number % 2 === 0;
}

assert.strictEqual(isEven(4), true, '4 is an even number');
assert.ok(isEven(4), '4 is an even number');

14.4.3 The throws() assertion method

throws(function[, expected][, message])
Parameters
function (Function)
expected (Object|Function|RegExp)
message (String)
Returns
undefined

function isEven(number) {
 if (typeof number !== 'number') {
 throw new Error('The passed argument is not a number');
 }
 return number % 2 === 0;
}

assert.throws(
 function() {
 isEven('test');
 },
 new Error('The passed argument is not a number'),
 'Passing a string throws an error'
);

14.5 How to test asynchronous tasks

async
Parameters
none
Returns
A unique resolution callback function.

QUnit.test('Testing asynchronous code', function(assert) {
 var $fixtures = $('#qunit-fixture');
 assert.expect(4);
 assert.strictEqual(
 $fixtures.children().length,
 0,
 'The children of qunit-fixtures are 0'
 );
 var firstCallback = assert.async();
 window.setTimeout(function() {
 assert.ok(isEven(4), '4 is even');
 firstCallback();
 }, 500);
 var secondCallback = assert.async();
 $fixtures.load('test.1.html #qunit', function() {
 assert.ok(
 true,
 'File test.1.html has been successfully loaded'
 );
 assert.strictEqual(
 $fixtures.children().length,
 1,
 'The elements appended to qunit-fixtures are 1'
);
 secondCallback();
 });
 });

14.6 noglobals and notrycatch

QUnit.test('Testing the noglobals option', function(assert) {
 assert.expect(1);
 window.bookName = 'jQuery in Action';
 assert.strictEqual(bookName, 'jQuery in Action', 'Strings are equal');
});

QUnit.test('Testing the notrycatch option', function(assert) {
 assert.expect(1);
 assert.strictEqual(add(2, 2), 4, 'The sum of 2 plus 2 is equal to 4');
});

14.7 Group your tests in modules

QUnit.module(name[, lifecycle])
Parameters
name (String)
lifecycle (Object)
Returns
undefined

QUnit.module('Core');
QUnit.test('First test', function(assert) {
 assert.expect(1);
 assert.ok(true);
});

QUnit.module('Ajax');
QUnit.test('Second test', function(assert) {
 assert.expect(1);
 assert.ok(true);
});

14.8 Configuring QUnit

The configuration properties of QUnit.config

QUnit.config.hidepassed = true;

QUnit.config.requireExpects = true;

14.9 An example test suite

14.10 Summary