The document discusses modular testing in JavaScript, emphasizing the importance and concepts of unit testing, including TDD (Test-Driven Development) and BDD (Behavior-Driven Development). It outlines various tools and libraries available for testing, such as Mocha, Jasmine, and Sinon, while highlighting best practices and key techniques like stubbing and mocking. The document serves as a comprehensive guide for implementing effective unit testing strategies in JavaScript development.

1. В поисках качества
JavaScript:
модульное тестирование
Анна Хабибуллина
DA-14 / da-14.com
anna.khabibullina@da-14.com
akhabibullina
_khabibullina

2. ZE QUALITYS?
“Any feature without a test doesn’t exist”
Steve Loughran HP Laboratories

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

4. 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.

5. WHY UNIT TESTING?
Unit tests find problems early in the
development cycle (TDD & BDD)
Refactoring
Integration
Documentation
Better design

6. 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

7. BASIC TERMS

8. In simple words, the goal of assertion is to
forcefully define if the test fails or passes.
STATEMENT PASSES FAILS
x = 1 assert(x > 0) assert(x < 0)
expect(4+5).to.equal(9);
ASSERTION

9. function initialize() {
// The initialization was successful.
return true;
}
Given the function initialize():
ASSERTION: EXAMPLE

10. ASSERTION: EXAMPLE
var isInitialized = initialize();
TDD assert.isTrue(isInitialized)
BDD expect(isInitialized).to.be.true
Check that function initialize() returns true
when called.

11. 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.

12. FIXTURE: EXAMPLE
Require the piece of markup stored in
myfixturemarkup.html file before each test:
beforeEach(function() {
loadFixtures('myfixturemarkup.html');
});

13. STUB
Method stubs
are functions
with pre-
programmed
behavior.

14. 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);

15. 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.

16. 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

17. MOCK
Mocks are fake objects with pre-
programmed behavior (like stubs) and
pre-programmed expectations.
They are like both stubs and spies – in
one.

18. 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);

19. 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?

20. TEST DRIVEN DEVELOPMENT(TDD)
TDD is a software
development
process that…
I’ll tell you the rest 

21. WHAT ARE THESE BDD?

22. ALRIGHT, WHAT IS BDD YOU ASK?
Terminology:
TDD BDD
Test Example
Assertion Expectation
Unit Behavior

23. BASIC STRUCTURE
#1. Setup/BeforeEach/Before
#2. Prepare an input
#3. Call a method
#4. Check an output
#5. Tear down/AfterEach/After

24. #1. Setup / Before
before(function(done) {
// Create a basic document.
document = jsdom.jsdom();
window = document.parentWindow;
done();
});
BASIC STRUCTURE: EXPLAINED

25. Before / BeforeEach
before(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 test
first test
after each test
second test
after each test
BASIC STRUCTURE: EXPLAINED

26. 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) {

27. 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) {

28. 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) {

29. 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) {

30. #5. TearDown / After
after(function(done) {
// Remove global objects document.
document = null;
window = null;
done();
});
BASIC STRUCTURE: EXPLAINED

31. OUTPUT

32. <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

33. <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

34. TOOLS

35. 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

36. ENTIRE SPACE OF FRAMEWORKS…

37. HOW DO I UNIT TEST
Known Frameworks / Libraries?
What to test? What to use?
Angular, React, Flight Karma + Jasmine
Backbone qUnit
Ember Karma + qUnit (ember-app-kit)
ExtJs Jasmine, Siesta (UI)
TypeScript tsUnit
CoffeeScript qUnit
Dart Unittest, Hop and Drone.io
NodeJs expresso and vows, Nodeunit

38. 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

39. TOOLS: WHAT WE USE

40. TOOLS: WHAT WE USE
Project unit tested like a dream ♥

41. UNIT TESTING SPECIFICS IN JAVASCRIPT
UI
Load fake data via “fixtures”
Jsdom(W3C JavaScript implementation)

42. UNIT TESTING SPECIFICS IN JAVASCRIPT
AJAX
Stub jQuery.ajax
Fake XMLHttpRequest
(XMLHTTP ActiveXObject)
Fake server

43. UNIT TESTING SPECIFICS IN JAVASCRIPT
3rd-party scripts
Stubbing jQuery plugin functions
(mock jQuery.fn)

44. UNIT TESTING SPECIFICS IN JAVASCRIPT
Dependency Injection
Mocking deps in RequireJs sucks hard!
Squire.js lib / testr.js

45. UNIT TESTING SPECIFICS IN JAVASCRIPT
NodeJs
Server-side specifics
rewire: node.js dependency injection

46. BEST PRACTISES
Fast
Isolated
Consistent
Responsibility
Self-descriptive
No exception Handling
Use assertions when needed

47. 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!

48. SHWEEET

49. ありがとう