Testing web APIs

jakobm.com
@jakobmattsson
I’m a coder first and foremost. I also help
companies recruit coders, train coders and
architect software. Sometimes I do technical
due diligence and speak at conferences.
!
Want more? Read my story or blog.

FishBrain is the fastest, easiest way
to log and share your ﬁshing.

!
Get instant updates from anglers on
nearby lakes, rivers, and the coast.

Testing web APIs
Simple and readable

Example - Testing a blog API
• Create a blog
• Create two blog entries
• Create two users
• Create a lotal of three comments from
those users, on the two posts
• Request the stats for the blog and
check if the given number of entries
and comments are correct

post('/blogs', {
name: 'My blog'
}, function(err, blog) {
! post(concatUrl('blogs', blog.id, 'entries'), {
title: 'my first post’,
body: 'Here is the text of my first post'
}, function(err, entry1) {
title: 'my second post’,
body: 'I do not know what to write any more...'
! post('/user', {
name: 'john doe’
}, function(err, visitor1) {
! post('/user', {
name: 'jane doe'
! post('/comments', {
userId: visitor1.id,
entryId: entry1.id,
text: "well written dude"
}, function(err, comment1) {
entryId: entry1.id,
text: "like it!"
entryId: entry2.id,
text: "nah, crap"
! get(concatUrl('blogs', blog.id), function(err, blogInfo) {
assertEquals(blogInfo, {
name: 'My blog',
numberOfEntries: 2,
numberOfComments: 3
});
});
});
});
});
});
});
});
});
});

*No, this is not a tutorial
Promises 101*

getJSON({
url: '/somewhere/over/the/rainbow',
success: function(result) {
// deal with it
}
});

getJSON({
// deal with it
}
});
rainbows.then(function(result) {
// deal with it
});
var rainbows = getJSON({
url: '/somewhere/over/the/rainbow'
});

getJSON({
// deal with it
}
});
rainbows.then(function(result) {
// deal with it
});
var rainbows = getJSON({
url: '/somewhere/over/the/rainbow'
});
f(rainbows);

Why is that
a good idea?
• Loosen up the coupling
• Superior error handling
• Simplified async

Why is that
a good idea?
• Loosen up the coupling
• Superior error handling
• Simplified async
But in particular, it abstracts away the temporal
dependencies in your program (or in this case, test)

That’s enough 101
(even though people barely talk about
the last - and most important - idea)

Promises are not new
http://github.com/kriskowal/q
http://www.html5rocks.com/en/tutorials/es6/promises
http://domenic.me/2012/10/14/youre-missing-the-point-of-promises
http://www.promisejs.org
https://github.com/bellbind/using-promise-q
https://github.com/tildeio/rsvp.js
https://github.com/cujojs/when

They’ve even
made it into ES6

They’ve even
made it into ES6
Already implemented
natively in
Firefox 30Chrome 33

So why are you not
using them?

1. Draw some
circles
How to draw an owl

1. Draw some
circles
2.Draw the rest
of the owl
How to draw an owl

We want to
draw owls.
!
Not circles.

getJSON('story.json').then(function(story) {
addHtmlToPage(story.heading);
!
// Map our array of chapter urls to
// an array of chapter json promises.
// This makes sture they all download parallel.
return story.chapterUrls.map(getJSON)
.reduce(function(sequence, chapterPromise) {
// Use reduce to chain the promises together,
// adding content to the page for each chapter
return sequence.then(function() {
// Wait for everything in the sequence so far,
// then wait for this chapter to arrive.
return chapterPromise;
}).then(function(chapter) {
addHtmlToPage(chapter.html);
});
}, Promise.resolve());
}).then(function() {
addTextToPage('All done');
}).catch(function(err) {
// catch any error that happened along the way
addTextToPage("Argh, broken: " + err.message);
}).then(function() {
document.querySelector('.spinner').style.display = 'none';
});
As announced
for ES6

That’s circles.
!
Nice circles!
!
Still circles.

browser.init({browserName:'chrome'}, function() {
browser.get("http://admc.io/wd/test-pages/guinea-pig.html", function() {
browser.title(function(err, title) {
title.should.include('WD');
browser.elementById('i am a link', function(err, el) {
browser.clickElement(el, function() {
browser.eval("window.location.href", function(err, href) {
href.should.include('guinea-pig2');
browser.quit();
});
});
});
});
});
});
Node.js WebDriver
Before promises

browser
.init({ browserName: 'chrome' })
.then(function() {
return browser.get("http://admc.io/wd/test-pages/guinea-pig.html");
})
.then(function() { return browser.title(); })
.then(function(title) {
title.should.include('WD');
return browser.elementById('i am a link');
})
.then(function(el) { return browser.clickElement(el); })
.then(function() {
return browser.eval("window.location.href");
})
.then(function(href) { href.should.include('guinea-pig2'); })
.fin(function() { return browser.quit(); })
.done();
After promises

Used to be
callback-hell.
!
Now it is
then-hell.

These examples are
just a diﬀerent way
of doing async.
!
It’s still uncomfortable.
It’s still circles!

!
Make async code
as straightforward
as sync code
The point of promises:

1 Promises out: Always return promises -
not callback
2 Promises in: Functions should accept
promises as well as regular values
3 Promises between: Augment promises as
you augment regular objects
Three requirements

Example - Testing a blog API
• Create a blog
• Create two blog entries
• Create some users
• Create some comments from those
users, on the two posts
• Request the stats for the blog and
check if the given number of entries
and comments are correct

post('/blogs', {
name: 'My blog'
title: 'my first post’,
title: 'my second post’,
! post('/user', {
name: 'john doe’
! post('/user', {
name: 'jane doe'
entryId: entry1.id,
entryId: entry1.id,
text: "like it!"
entryId: entry2.id,
text: "nah, crap"
name: 'My blog',
numberOfEntries: 2,
numberOfComments: 3
});
});
});
});
});
});
});
});
});
});
https://
github.com/
jakobmattsson/
z-presentation/
blob/master/
promises-in-out/
1-naive.js
1
Note: without narration, this slide lacks a lot of
context. Open the file above and read the
commented version for the full story.

post('/blogs', {
name: 'My blog'
! var entryData = [{
title: 'my first post',
}, {
title: 'my second post',
}]
! async.forEach(entryData, function(entry, callback), {
post(concatUrl('blogs', blog.id, 'entries'), entry, callback);
}, function(err, entries) {
! var usernames = ['john doe', 'jane doe'];
! async.forEach(usernames, function(user, callback) {
post('/user', { name: user }, callback);
}, function(err, visitors) {
! var commentsData = [{
userId: visitor[0].id,
entryId: entries[0].id,
}, {
text: "like it!"
}, {
text: "nah, crap"
}];
! async.forEach(commentsData, function(comment, callback) {
post('/comments', comment, callback);
}, function(err, comments) {
! assertEquals(blogInfo, {
name: 'My blog',
numberOfEntries: 2,
numberOfComments: 3
});
});
});
});
});
});
https://
github.com/
jakobmattsson/
z-presentation/
blob/master/
promises-in-out/
2-async.js
2

https://
github.com/
jakobmattsson/
z-presentation/
blob/master/
promises-in-out/
3-async-more-parallel.js
3
post('/blogs', {
name: 'My blog'
! async.parallel([
function(callback) {
var entryData = [{
}, {
}];
async.forEach(entryData, function(entry, callback), {
post(concatUrl('blogs', blog.id, 'entries'), entry, callback);
}, callback);
},
function(callback) {
var usernames = ['john doe', 'jane doe’];
async.forEach(usernames, function(user, callback) {
post('/user', { name: user }, callback);
}, callback);
}
], function(err, results) {
! var entries = results[0];
var visitors = results[1];
! var commentsData = [{
userId: visitors[0].id,
}, {
text: "like it!"
}, {
text: "nah, crap"
}];
! async.forEach(commentsData, function(comment, callback) {
post('/comments', comment, callback);
}, function(err, comments) {
name: 'My blog',
numberOfEntries: 2,
numberOfComments: 3
});
});
});
});
});

post('/blogs', {
name: 'My blog'
}).then(function(blog) {
! var visitor1 = post('/user', {
name: 'john doe'
});
! var visitor2 = post('/user', {
name: 'jane doe'
});
! var entry1 = post(concatUrl('blogs', blog.id, 'entries'), {
});
! var entry2 = post(concatUrl('blogs', blog.id, 'entries'), {
});
! var comment1 = all(entry1, visitor1).then(function(e1, v1) {
post('/comments', {
userId: v1.id,
entryId: e1.id,
});
});
post('/comments', {
userId: v2.id,
entryId: e1.id,
text: "like it!"
});
});
post('/comments', {
userId: v2.id,
entryId: e2.id,
text: "nah, crap"
});
});
! all(comment1, comment2, comment3).then(function() {
get(concatUrl('blogs', blog.id)).then(function(blogInfo) {
name: 'My blog',
numberOfEntries: 2,
numberOfComments: 3
});
});
});
});
https://
github.com/
jakobmattsson/
z-presentation/
blob/master/
promises-in-out/
4-promises-convoluted.js
4

1 Promises out: Always return promises -
not callback
2 Promises in: Functions should accept
promises as well as regular values
Three requirements

Augmenting objects
is a sensitive topic

Extending prototypes
!
vs
!
wrapping objects

You’re writing Course of action
An app Do whatever you want
A library
Do not modify the 
damn prototypes
Complimentary
decision matrix

Promises are already
wrapped objects

_(names)
.chain()
.unique()
.shuffle()
.first(3)
.value()
Chaining usually requires a
method to ”unwrap”
or repeated wrapping
u = _(names).unique()
s = _(u).shuffle()
f = _(s).first(3)

Promises already have a
well-defined way of
unwrapping.

_(names)
.unique()
.shuffle()
.first(3)
.then(function(values) {
// do stuff with values...
})
If underscore/lodash
wrapped promises

1 Deep resolution: Resolve any kind of
object/array/promise/values/whatever
2 Make functions promise-friendly: Sync or
async doesn’t matter; will accept promises
3 Augmentation for promises: jQuery/
underscore/lodash-like extensions
What is Z?

Deep resolution
var data = {
text: 'well written dude'
};
!
Z(data).then(function(result) {
!
// result is now: {
// userId: 123,
// entryId: 456,
// text: 'well written dude'
// }
!
});
Takes any object
and resolves all
promises in it.
!
Like Q and Q.all,
but deep
1

Promise-friendly functions
var post = function(url, data, callback) {
// POSTs `data` to `url` and
// then invokes `callback`
};
!
post = Z.bindAsync(post);
!
var comment1 = post('/comments', {
text: 'well written dude'
});
bindAsync creates
a function that
takes promises as
arguments and
returns a promise.
2

Promise-friendly functions
var add = function(x, y) {
return x + y;
};
!
add = Z.bindSync(add);
!
var sum = add(v1.get('id'), e1.get('id'));
!
var comment1 = post('/comments', {
text: 'well written dude',
likes: sum
});
2
bindSync does that
same, for functions
that are not async

Augmentation for promises
var commentData = get('/comments/42');
!
var text = commentData.get('text');
!
var lowerCased = text.then(function(text) {
return text.toLowerCase();
});
3
Without
augmentation
every operation
has to be wrapped
in ”then”

Z.mixin({
toLowerCase: function() {
return this.value.toLowerCase();
}
});
!
var commentData = get('/comments/42');
!
commentData.get('text').toLowerCase();
3
Z has mixin to
solve this
!
Note that Z is not
explicitly applied
to the promise

Z.mixin(zUnderscore);
Z.mixin(zBuiltins);
!
var comment = get('/comments/42');
!
comment.get('text').toLowerCase().first(5);
3
There are prepared
packages to mixin
entire libraries

Make async code
as straightforward
as sync code
Enough with
the madness

You don’t need a lib
to do these things

www.jakobm.com @jakobmattsson
!
github.com/jakobmattsson/z-core
Testing web APIs
Simple and readable

Testing web APIs

More Related Content

What's hot (20)

Viewers also liked (9)

Similar to Testing web APIs (20)

More from FDConf (20)

Recently uploaded (20)

Testing web APIs