painless javascript unit testing
DESCRIPTION
Some javascript testing patterns that has made writing tests at Refinery29 more maintainable. Covered in this presentation is userContext (or let) in Jasmine, lazy evaluation and shared behavior.TRANSCRIPT
PAINLESS JAVASCRIPT UNIT TESTING
The Presenters
@traviskaufman @benmidi
Setup
Introduction Structure Patterns Resources
Setup
Introduction Structure Patterns Resources
Setup
Introduction Patterns ResourcesStructure
Setup
Introduction Structure Patterns Resources
Introduction
Team Bicycle
● A Director of Product and Two developers
● Behavior Driven Development and Pairing
● Launched the new mobile web experience in 5 months
● 1000 Unit Tests and 200 Acceptance Tests
IntroductionPairing How many times have you been here?
IntroductionPairing Warning: They may laugh at you.
Introduction
Team Bicycle
● A Director of Product and Two developers
● Behavior Driven Development and Pairing
● Launched the new mobile web experience in 5 months
● 1000 Unit Tests and 200 Acceptance Tests
A team built for speed.
IntroductionProduct As close to native as possible. http://www.refinery29.com
Structure Grunt sets up tasks for running tests, example: grunt specs:debug
Gruntfile.js # Grunt for automating test runs
karma.conf.js # Karma for unit testing (Chrome for debugging, PhantomJS for CI builds in Jenkins)
app/ | js/| | models/| | **/*.js| | views/| | **/*.jsspec/| js/| | models/| | **/*_spec.js| | views/| | **/*_spec.js
Structure Karma sets up our testing environments. Great for running tests on actual devices.
Gruntfile.js # Grunt for automating test runs
karma.conf.js # Karma for unit testing (Chrome for debugging, PhantomJS for CI builds in Jenkins)
app/ | js/| | models/| | **/*.js| | views/| | **/*.jsspec/| js/| | models/| | **/*_spec.js| | views/| | **/*_spec.js
Structure The spec/ directory mirrors app/
Gruntfile.js # Grunt for automating test runs
karma.conf.js # Karma for unit testing
app/ | js/| | models/| | **/*.js| | views/| | **/*.jsspec/| js/| | models/| | **/*_spec.js| | views/| | **/*_spec.js
Structure Inside of spec/ is the helpers/ directory for global setup/tear down, mocks, convenience functions and custom Jasmine matchers.
Gruntfile.js # Grunt for automating test runs
karma.conf.js # Karma for unit testing
app/| js/| | models/| | **/*.js| | views/| | **/*.jsspec/| helpers/| | *.js # Helper files loaded in Karma| js/| | models/| | **/*_spec.js| | views/| | **/*_spec.js
Structure Our rspec acceptance tests also live in spec/
Gruntfile.js # Grunt for automating test runs
karma.conf.js # Karma for unit testing
app/| js/| | models/| | **/*.js| | views/| | **/*.jsspec/| helpers/| | *.js # Helper files loaded in Karma| js/| | models/| | **/*_spec.js| | views/| | **/*_spec.js| features/| | *_spec.rb| | spec_helper.rb| | support/| | **/*.rb
PatternsDRY it up
describe('views.card', function() {
var model, view;
beforeEach(function() {
model = {};
view = new CardView(model);
});
describe('.render', function() {
beforeEach(function() {
model.title = 'An Article';
view.render();
});
it('creates a "cardTitle" h3 tag set to the model\'s title', function() {
expect(view.$el.find('.cardTitle')).toContainText(model.title);
});
});
describe('when the model card type is "author_card"', function() {
beforeEach(function() {
model.type = 'author_card';
view.render();
});
it('adds an "authorCard" class to it\'s $el', function() {
expect(view.$el).toHaveClass('authorCard');
});
});
});
PatternsUsing this
describe('views.card', function() {
beforeEach(function() {
this.model = {};
this.view = new CardView(this.model);
});
describe('.render', function() {
beforeEach(function() {
this.model.title = 'An Article';
this.view.render();
});
it('creates a "cardTitle" h3 tag set to the model\'s title', function() {
expect(this.view.$el.find('.cardTitle')).toContainText(this.model.title);
});
});
describe('when the model card type is "author_card"', function() {
beforeEach(function() {
this.model.type = 'author_card';
this.view.render();
});
it('adds an "authorCard" class to it\'s $el', function() {
expect(this.view.$el).toHaveClass('authorCard');
});
});
});
PatternsUsing this
Jasmine’s userContext (aka this)
● Shared between before/afterEach hooks and tests (including nested tests)
● Cleaned up after every test
● Removes the need for keeping track of variable declarations
● Removes problems that may occur due to scoping and/or hoisting issues
● No global leaks
● Clearer meaning within tests
● Leads the way to...
PatternsLazy Eval
beforeEach(function() {
this.let_ = function(propName, getter) { // need to use "_" suffix since 'let' is a token in ES6
var _lazy;
Object.defineProperty(this, propName, {
get: function() {
if (!_lazy) {
_lazy = getter.call(this);
}
return _lazy;
},
set: function() {},
enumerable: true,
configurable: true
});
};
});
Lazy Evaluation (a la Rspec’s let)
describe('.render', function() {
beforeEach(function() {
this.let_('renderedView', function() {
return this.view.render();
});
this.model.title = 'An Article';
});
// ...
PatternsLazy Eval
describe('views.Card', function() {
beforeEach(function() {
this.model = {};
this.view = new CardView(this.model);
});
describe('.render', function() {
beforeEach(function() {
this.model.title = 'An Article';
this.let_('renderedView', function() {
return this.view.render();
});
});
it('creates a "cardTitle" h3 tag set to the model\'s title', function() {
expect(this.renderedView.$el.find('.cardTitle')).toContainText(this.model.title);
});
describe('when the model card type is "author_card"', function() {
beforeEach(function() {
this.model.type = 'author_card'; // no need to re-render the view here!
});
it('adds an "authorCard" class to its $el', function() {
expect(this.renderedView.$el).toHaveClass('authorCard');
});
// ...
PatternsLazy Eval
Lazy Evaluation
● Our render spec, now uses let_
● We only have to call render once, in the getter function, even if we change the model in nested beforeEach blocks
● Reduced code duplication
● Reduced chance of pollution due to side effects
● Smaller file sizes!
● Note: everything here can be used for Mocha as well!
PatternsBehaves Like
describe('Email', function() {
beforeEach(function() {
this.emailAddress = '[email protected]';
this.let_('email', function() {
return new Email(this.emailAddress);
});
});
describe('.validate', function() {
describe('when emailAddress is missing the "@" symbol', function() {
beforeEach(function() {
this.emailAddress = 'someexample.com';
});
it('returns false', function() {
expect(this.email.validate()).toBe(false);
});
});
describe('when emailAddress is missing a domain after the "@" symbol', function() {
beforeEach(function() {
this.emailAddress = '[email protected]';
});
it('returns false', function() {
expect(this.email.validate()).toBe(false);
});
});
});
});
PatternsBehaves Like
Shared Behavior
● Thorough, but lots of copy-pasta code
● If API changes, all tests have to be updated
○ e.g. what if validate changes to return a string?
● RSpec solves this with “shared examples”
● Need something like that here...
PatternsBehaves Like
describe('Email', function() {
beforeEach(function() {
this.emailAddress = '[email protected]';
this.let_('email', function() {
return new Email(this.emailAddress);
});
});
describe('.validate', function() {
shouldInvalidate('an email without an "@" sign', 'someexample.org');
shouldInvalidate('missing a domain', '[email protected]');
//..
function shouldInvalidate(desc, example) {
describe('when emailAddress is ' + desc, function() {
beforeEach(function() {
this.emailAddress = example;
});
it('returns false', function() {
expect(this.email.validate()).toBe(false);
});
});
}
});
});
PatternsBehaves Like
Shared Behavior
● No more duplication of testing logic
● Extremely readable
● Leverage this along with javascripts metaprogramming techniques to create dynamically built suites
● Looks great in the console
● Completely DRY
● Huge win for something like email validation, where there are tons of cases to test
● Prevents having one test with a large amount of assertions
Resources
We’re Hiring
Front-End Engineer | Full Time
QA Engineer | Full Time
Developer Tools & Automation Engineer | Full Time
Junior DevOps Engineer | Full Time
Desktop Support Engineer | Full Time
Back-End Engineer | Full Time
Resources
Links
● Our Blog: http://j.mp/R29MobileBlog
● Travis’ Gist on userContext: http://bit.ly/BetterJasmine
● Slides:http://bit.ly/JSStackUp
Thanks!