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Meet Slobodan
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Build with
serverless! Its me!
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No server
management / ops
Scales per use
Autofailover
Don’t pay
for idle
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Business is more
profitable
Faster delivery
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Code needs to run on
servers!
Serverless?
That’s not
the point!
You’re an idiot
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It is serverless,
the same way WIFI is wireless.
Gojko Adzic
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Ok, lets try…
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AWS
Lambda
DynamoDB
API Gateway AWS S3
To learn…
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…the way it has changed…
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to build…
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…a functioning product
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Accidents do happen
Something will break…
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…the business suffers
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How do I prevent
this? You test!
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We don’t have
time to test! The you will find
time to fix!
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Ok, how do I test a
serverless app?
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Testing Serverless
Applications
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Aleksandar Simovic
Senior Software Engineer @ ScienceExchange
AWS Serverless Hero
coauthor of “Serverless Applications with Node.js” book
AWS SAM & Lambda Builders Contributor
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Why do you test?
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• “Industry standard”.
• “90% test coverage is required.”
• “Code compliance”.
• “You need to ensure that the code works”.
The Usual replies
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• “I don’t know, my CTO told me”
• “I read HackerNews, I want to look smart”
• “Because DHH said that.”
• “Ensure quality.”
The “real” replies
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All
(somewhat)
valid responses
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The purpose of Testing
is to find and prevent
defects.
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• John Null
• E Lee
• GoVeg.com
But Testing only to find or prevent
defects is not enough
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One of the purposes of testing is to
Reduce Risk
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What are these risks
when building serverless
applications?
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First, the way we build
applications has changed
with serverless
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Its risks…
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• configuration risks
• technical workflow risks
• business logic risks
• integration risks
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Configuration
risks
Receiving events from the
correct API?
Access rights?
Saving to correct
bucket?
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Technical
workflow risks
Handling success / error
workflow responses
Are we using the
incoming events
correctly?
Workflow risks
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Business logic
risks
What is the
correct structure
of our data
By which order do
we process our
data?
Is the file
conversion
correct? Are we saving in a correct
folder in the bucket?
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Integration risks
Are our AppSync
GraphQL objects
properly set in
DynamoDB?
Are we reading AND
writing events from API
Gateway to S3 correctly?
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How do we address those risks
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Good Architecture
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What is a good architecture for
serverless?
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Hexagonal Architecture
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Alistair Cockburn
Allow an application to equally be driven by
users, programs, automated test or batch
scripts, and to be developed and tested in
isolation from its eventual run-time devices
and databases.
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Boooring!
Show me an example
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const AWS = require('aws-sdk'),
stripe = require('stripe'),
qs = require('querystring'),
processResponse = require('./process-response'),
stripe = require('stripe')(process.env.STRIPE_SECRET_KEY);
exports.handler = async (event) => {
if (!event.body) {
return processResponse('invalid', 400);
}
const newCharge = qs.parse(event.body);
if (!newCharge.amount || !newCharge.currency) {
return 'invalid arguments, please provide amount and currency fields as
mentioned in the app README';
}
return await stripe.charges.create({
source: newCharge.stripeToken,
amount: newCharge.amount,
currency: newCharge.currency,
description: 'Charge Description'
})
};
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Separate interface risk
from your
Business logic risk
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In code..
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const pubsubRepository = require('./pubsub-repository'),
paymentProcessorRepository = require('./payment-processor'),
TOPIC_ARN = process.env.TOPIC_ARN;
module.exports = async function chargeCustomer(
secretKey,
token,
email,
amount,
currency,
description = 'Charge Description',
paymentProcessor = paymentProcessorRepository,
pubsub = pubsubRepository,
subject = TOPIC_ARN
){
const createdCharge = await paymentProcessor.createCharge(secretKey, token,
amount, currency, description);
createdCharge.email = email;
await pubsub.publish(createdCharge, subject);
return createdCharge;
}
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const AWS = require('aws-sdk'),
sns = new AWS.SNS(),
NO_DATA_REPLY = 'You must provide data to the your PubSub';
module.exports = {
publish: async function publish(
data,
topic,
pubSub = sns
){
return await pubSub.publish({
Message: JSON.stringify(data),
TopicArn: topic
}).promise();
}
};
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What do I test in a
serverless app?
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What do you test in
a traditional app?
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What is different
in a serverless app?
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Managed (and cheaper)
infrastructure,
many smaller business logic pieces
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Even though with serverless
your infrastructure is
managed
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That doesn’t mean your code
is managed as well!
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Integration tests are cheaper,
but also more important,
because a common serverless app is
split into many small pieces
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Testing your code and your
integrations is now more
important than before!
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I know the
“Why”, “risks”, “What”…
But now I need
the “How”?
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How to test serverless
applications
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Just show me how
in practice.
Wait!
Stop using long
words…
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First, the tools!
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Tools
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• Jest
• Jasmine
• Mocha
• Cypress
• any other popular tool
For example, for Node.js you can use:
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Testing is very important on
all levels both unit, integrated
and end-to-end-testing.
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Unit and
integration tests!
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Sample unit test
code
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const convertFromSentry = require('../src/convert-from-sentry'),
lambdaProxyEvent = require('./test-events/lambda-proxy-event'),
wrapEvent = (event) => {
const result = JSON.parse(JSON.stringify(lambdaProxyEvent));
result.body = JSON.stringify(event);
return result;
};
describe('Convert from Sentry', () => {
describe('Error type', () => {
test('should pickup the error type if defined', () => {
const event = wrapEvent(require('./test-events/raven-exception'));
expect(convertFromSentry(event).type).toBe('TypeError');
});
test('should use runtime error type if undefined', () => {
const event = wrapEvent(require('./test-events/raven-manually-tracked'));
expect(convertFromSentry(event).type).toBe('RuntimeError');
});
});
describe('Error message', () => {
test('should pickup the message if exception value defined', () => {
const event = wrapEvent(require('./test-events/raven-exception'));
expect(convertFromSentry(event).message).toBe(`Cannot read property 'captureException' of
undefined`);
});
test('should use body message if exception value undefined', () => {
const event = wrapEvent(require('./test-events/raven-manually-tracked'));
expect(convertFromSentry(event).message).toBe('error');
});
});
});
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• hexagonal architecture
• be smart
• test integrations that you own
• or test your code with a different adapter
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If you test and properly design
using Hexagonal architecture
you’re even out of “vendor lock-in”.
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UI testing
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Benefits of serverless are
cheap infrastructure and easy
fast parallelization.
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What about CI/CD?
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It works the same way as it did
with any other app
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Use your favorite deployment tool from CI
to deploy your serverless app
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• Jenkins
• Travis CI
• AWS CodePipeline
• Semaphore CI
• CircleCI
• and many more
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Testing
environments?
And what about…
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Having test environments was never cheaper
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Automate deployment from git branches to
different stages
(ie. production, dev, staging, qa)
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Testing slows you
down!
You’re making it
sound too easy…
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Actually…
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Testing your serverless
apps quickens your
software delivery even more.
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Real life example
@
ScienceExchange
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Hexagonal Architecture
3 months > 2 weeks
Unit / Integration testing
+
=
Going serverless
+
$40,000 > $10
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• Testing your serverless applications is
more important than ever
• One of the goals of testing is to reduce risk
• use Hexagonal Architecture to stay flexible
• serverless helps testers to do their job faster and cheaper
• Testing serverless applications speeds up delivery
Key takeaways
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serverless.pub/book
“Serverless Applications
with Node.js"
@simalexan
claudia40
40% off
Thank you!