В поисках качества JavaScript:модульное тестированиеАнна ХабибуллинаDA-14 / da-14.com

anna.khabibullina@da-14.com

akhabibullina

_khabibullina

ZE QUALITYS?

“Any feature without a test doesn’t exist”

Steve Loughran HP Laboratories

AGENDA

Unit Testing Concept Pros & Cons Basic Terms & Structure TDD &/vs. BDD Tools & Libraries Unit Testing Specifics in JavaScript Best Practices

UNIT TESTING CONCEPT

Unit testing is a method by which individual units of source code are tested to determine

if they are fit for use.

WHY UNIT TESTING?

Unit tests find problems early in the development cycle (TDD & BDD)

Refactoring

Integration

Documentation

Better design

IS UNIT TESTING A GOOD INVESTMENT?

slow down the development process

share the same blind spots with the code

doesn’t prove that they’re compatible with one another or configured correctly

BASIC TERMS

In simple words, the goal of assertion is to forcefully define if the test fails or passes.

STATEMENT PASSES FAILSx = 1 assert(x > 0) assert(x < 0)

expect(4+5).to.equal(9);

ASSERTION

function initialize() {

// The initialization was successful. return true;}

Given the function initialize():

ASSERTION: EXAMPLE

ASSERTION: EXAMPLE

var isInitialized = initialize();

TDD assert.isTrue(isInitialized)BDD expect(isInitialized).to.be.true

Check that function initialize() returns true when called.

FIXTURE

A test fixture is a fixed state of the software under test used as a baseline for running tests. In JavaScript for client side:

simulate AJAX responses;loading known set of data such as html objects.

FIXTURE: EXAMPLE

Require the piece of markup stored in myfixturemarkup.html file before each test:

beforeEach(function() {

loadFixtures('myfixturemarkup.html');

});

STUB

Method stubs are functions

with pre-programmed

behavior.

STUB: EXAMPLE

Forcing a method to throw an error in order to test error handling.

var fn = foo.stub().throws(Error);

expect(fn).to.throw(Error);

SPY

A test spy is a function that

records arguments,

return value, the value of this and exception thrown (if any) for all its

calls.

SPY: EXAMPLE

Test that a function cursor.hide() has been only called once, and only once.

sinon.spy(cursor, "hide");

TDD sinon.assert.calledOnce(cursor.hide) BDD expect(cursor.hide.calledOnce).to.be.true

MOCK

Mocks are fake objects with pre-programmed behavior (like stubs) and

pre-programmed expectations.They are like both stubs and spies – in

one.

MOCK: EXAMPLE

Create an expectation that jQuery.each is called once, and only once, and also instructs the mock to behave as we pre-define.

var mock = sinon.mock(jQuery);

MOCK: EXAMPLE

#1 – which method?#2 – how many times it is called?#3 – what are the arguments when the method called?#4 – what the method returns?

TEST DRIVEN DEVELOPMENT(TDD)

TDD is a software development process that…I’ll tell you the rest

WHAT ARE THESE BDD?

ALRIGHT, WHAT IS BDD YOU ASK?

Terminology:

TDD BDDTest ExampleAssertion ExpectationUnit Behavior

BASIC STRUCTURE

#1. Setup/BeforeEach/Before

#2. Prepare an input

#3. Call a method

#4. Check an output

#5. Tear down/AfterEach/After

#1. Setup / Before

before(function(done) { // Create a basic document. document = jsdom.jsdom(); window = document.parentWindow; done(); });

BASIC STRUCTURE: EXPLAINED

Before / BeforeEachbefore(function() { console.log(‘before test’); });

test(‘first test’, function() { console.log(‘first test’); });

test(‘second test’, function() { console.log(‘second test’);});

afterEach(function() { console.log(‘after each test’); });

Result

before testfirst testafter each testsecond testafter each test

BASIC STRUCTURE: EXPLAINED

BASIC STRUCTURE: EXPLAINED

it('should initialize cursor if zoom level >= minimum zoom level.',

#2. Prepare an input and predicted result. var minZoomLevel = 1; var zoomLevel = minZoomLevel + 0.1; var expectedCursor = {‘color’: ‘white’, ‘height’: … };

#3. Call a method. var actualCursor = cursor.init(zoomLevel);

#4. Check an output. expect(actualCursor).to.deep.equal(expectedCursor); done();

});

function(done) {

BASIC STRUCTURE: EXPLAINED

it('should initialize cursor if zoom level >= minimum zoom level.',

#2. Prepare an input and predicted result. var minZoomLevel = 1; var zoomLevel = minZoomLevel + 0.1; var expectedCursor = {‘color’: ‘white’, ‘height’: … };

#3. Call a method. var actualCursor = cursor.init(zoomLevel);

#4. Check an output. expect(actualCursor).to.deep.equal(expectedCursor); done();

});

function(done) {

BASIC STRUCTURE: EXPLAINED

it('should initialize cursor if zoom level >= minimum zoom level.',

#2. Prepare an input and predicted result. var minZoomLevel = 1; var zoomLevel = minZoomLevel + 0.1; var expectedCursor = {‘color’: ‘white’, ‘height’: … };

#3. Call a method. var actualCursor = cursor.init(zoomLevel);

#4. Check an output. expect(actualCursor).to.deep.equal(expectedCursor); done();

});

function(done) {

BASIC STRUCTURE: EXPLAINED

it('should initialize cursor if zoom level >= minimum zoom level.',

#2. Prepare an input and predicted result. var minZoomLevel = 1; var zoomLevel = minZoomLevel + 0.1; var expectedCursor = {‘color’: ‘white’, ‘height’: … };

#3. Call a method. var actualCursor = cursor.init(zoomLevel);

#4. Check an output. expect(actualCursor).to.deep.equal(expectedCursor); done();

});

function(done) {

#5. TearDown / After

after(function(done) {// Remove global objects document. document = null; window = null;done();

});

BASIC STRUCTURE: EXPLAINED

OUTPUT

<testsuite name="Macchiato Tests" tests="13" failures="0" errors="0" skipped="0" timestamp="Mon, 02 Dec 2013 11:08:09 GMT" time="0.114">

<testcase classname = "cursor #init ()" name = "should initialize cursor if zoom level &gt; minimum zoom level." time="0.004"/>

</testsuite>

OUTPUT: SUCCESS

<failure classname="cursor #init()" name="should initialize cursor if zoom level &gt; minimum zoom level." time="0" message="Cannot read property 'show' of undefined"><![CDATA[TypeError: Cannot read property 'show' of undefined

// ..... Exception Stack Trace .....

</failure>

OUTPUT: FAILURE

TOOLS

TOOLS

> 40 frameworks & libraries

qUnit(TDD) light-weight TDD framework

Jasmine(BDD) flexible BDD framework

Mocha / Karma test runner for async code

+ Chai TDD / BDD assertion library

+ Sinon test spies, stubs & mocks

ENTIRE SPACE OF FRAMEWORKS…

HOW DO I UNIT TEST Known Frameworks / Libraries?

What to test? What to use?Angular, React, Flight Karma + JasmineBackbone qUnitEmber Karma + qUnit (ember-app-kit)ExtJs Jasmine, Siesta (UI)TypeScript tsUnitCoffeeScript qUnitDart Unittest, Hop and Drone.io

NodeJs expresso and vows, Nodeunit 

TOOLS: WHAT WE USE

Run UT: Mocha Run UT in parallel: Macchiato Assert/Expect: Chai W3C DOM in JavaScript: Jsdom Mock, spy, stub: Sinon Code coverage tool: None Routine automation: make/Grunt

TOOLS: WHAT WE USE

TOOLS: WHAT WE USE

Project unit tested like a dream ♥

UNIT TESTING SPECIFICS IN JAVASCRIPT

UI

Load fake data via “fixtures”Jsdom(W3C JavaScript implementation)

UNIT TESTING SPECIFICS IN JAVASCRIPT

AJAX

Stub jQuery.ajaxFake XMLHttpRequest

(XMLHTTP ActiveXObject)Fake server

UNIT TESTING SPECIFICS IN JAVASCRIPT

3rd-party scripts

Stubbing jQuery plugin functions(mock jQuery.fn)

UNIT TESTING SPECIFICS IN JAVASCRIPT

Dependency Injection

Mocking deps in RequireJs sucks hard! Squire.js lib /  testr.js 

UNIT TESTING SPECIFICS IN JAVASCRIPT

NodeJs

Server-side specificsrewire: node.js dependency injection

BEST PRACTISES

FastIsolatedConsistentResponsibilitySelf-descriptiveNo exception HandlingUse assertions when needed

WRAPPING UP

Each test verifies a small chunk of code

Unit tests work best in isolation Mocks, stubs and spies help to

isolate test Don’t test everything but write

many tests > 40 tools are available to ease

unit testing experience, so CHOOSE YOUR OWN!

SHWEEET

ありがとう