Testing Serverless Applications @ Serverless Days Tel Aviv

@slobodan_ Are you testing your apps?

@slobodan_ !

@slobodan_ How do you test your apps?

@slobodan_ • Automated testing? • Manual testing? • Manual testing
by your end users?* * Also known as testing in production

@slobodan_ But, why do we test our apps?

Testing Serverless Applications

@slobodan_ Meet Alex

@slobodan_

@slobodan_ Try serverless! AWS Lambda!

@slobodan_

@slobodan_ Server

@slobodan_ Server OS

@slobodan_ Server OS Platform

@slobodan_ Server OS Platform App

@slobodan_

@slobodan_ But, there are servers in serverless, right?

@slobodan_ "It is serverless the same way WIFI is wireless."
Gojko Adzic  Bond villain

@slobodan_

@slobodan_ But how do they fit serverless in their common
development process?

@slobodan_

@slobodan_ Let's try!

@slobodan_

@slobodan_ Before we continue!

@slobodan_ Meet Slobodan

Slobodan Stojanovic CTO @ Cloud Horizon CTO @ VacationTracker.io co-author
of Serverless Applications with Node.js book @slobodan_

@slobodan_ AWS Serverless Hero

@slobodan_ What about our development process?

@slobodan_ Running a serverless app locally * CHAPTER 1 *

@slobodan_ Can we run our serverless app locally?

@slobodan_ YES and NO

@slobodan_ Tooling is better and better!

@slobodan_ • Azure Functions Core Tools (for Azure functions) •
AWS SAM CLI (for AWS SAM) • Third-party tools (ie. localstack) • docker-lambda for AWS Lambda local simulation • Run Node.js function locally • And more…

@slobodan_ But is hard to simulate everything!   For example,
permissions, AWS Cognito or Kinesis?

@slobodan_ You can run parts of your code locally to
speed up the development, but not everything

@slobodan_ However, you can have one environment per developer.  
It's cheap and easy to setup.

@slobodan_ Can we do better?

@slobodan_ Yes. Write tests!

@slobodan_

@slobodan_ Automated testing * CHAPTER 2 *

@slobodan_ Why do we need to test serverless application?

@slobodan_ !

@slobodan_ Why do you test any application?

@slobodan_ What tools can we use to test our serverless
app?

@slobodan_ You can use tools that you are already using
for non-serverless apps

@slobodan_ For example,  for Node.js you can use Jest, Mocha,
Cypress, etc.

@slobodan_ What should we test in a serverless app?

@slobodan_ Testing pyramid

@slobodan_

@slobodan_ Testing pyramid vs "Serverless testing pyramid"

@slobodan_

@slobodan_ Integration tests are cheaper, but also more important! Because
common serverless app is split into many small pieces

@slobodan_ How do we write testable serverless apps?

@slobodan_ • configuration risks • technical workflow risks • business
logic risks • integration risks

@slobodan_ Handle risks with good architecture

@slobodan_ Ok, but which architecture is good for serverless?

@slobodan_ Any architecture that will let you test your serverless
app easily and keep switching costs low.

@slobodan_ Because sooner or later you'll need to switch/migrate pieces
of your app.

@slobodan_ Not to another cloud vendor, but to your new
service, new or changed integration…

@slobodan_ For example, Hexagonal architecture or  Ports and adapters

@slobodan_ "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." Alistair Cockburn  Creator of Hexagonal architecture

@slobodan_

@slobodan_ Do you have an example?

@slobodan_

@slobodan_ Code, please.

@slobodan_ const {  httpResponse, parseApiEvent,  SnsRepository  } = require('../common')  const
main = require('./main')  async function handler(event) { const { body, headers } = parseApiEvent(event) // Create instance of SNS notification repository  const notification = new SnsRepository(  process.env.topic ) // Invoke main function with all dependencies  await main(body, headers, notification)  return httpResponse()  }

@slobodan_ await main(body, headers, notification)

@slobodan_ Unit tests

@slobodan_ await main(body, headers, mockNotification) Mock notification repository instance Some
static values

@slobodan_ Integration tests

@slobodan_ await main(body, headers, localNotification) Local notification adapter, using JS
events for example Some static values

@slobodan_ What about UI and end-to-end tests?

@slobodan_ Serverless is mainly a back end thing, but it
can help with UI tests!

@slobodan_ UI tests are slow and expensive

@slobodan_ Benefits of serverless are cheap infrastructure and easy/fast parallelization

@slobodan_

@slobodan_ What about tools?

@slobodan_ • cypress • puppeteer • appraise.qa • and others…

@slobodan_

@slobodan_ What about CI/CD?

@slobodan_ CI / CD * CHAPTER 3 *

@slobodan_ It works the same way as any other app

@slobodan_ Use your favorite deployment tool from CI to deploy
your serverless app

@slobodan_ However, be careful with your secrets (i.e., access and
secret keys)

@slobodan_ You can automate deployment from git branches to different
stages (ie. production, dev, staging, qa)

@slobodan_

@slobodan_ Nothing changes for manual testing?

@slobodan_ Quality Assurance (QA) * CHAPTER 4 *

@slobodan_ Stages and deployments are cheap and often fast to
setup

@slobodan_ You don't pay for your app infrastructure if no-one
is using it

@slobodan_ Having multiple test environments was never cheaper!

@slobodan_ Bonus: You can promote tested function to production!

@slobodan_

@slobodan_ And they lived happily ever after…

@slobodan_

@slobodan_ Risks and challenges

@slobodan_ Deployment risk

@slobodan_ Units are smaller and easier to test, but deployment,
triggers and permissions are not trivial

@slobodan_ You should use well tested and mature deployment tool

@slobodan_ What are popular deployment tools?

@slobodan_ • AWS SAM • AWS CDK • Serverless Framework
• Claudia.js • .architect • and many others

@slobodan_ Integration errors and changes

@slobodan_ Your app might just work*, but integrations can change
and cause failures

@slobodan_ How do you make sure they don't?

@slobodan_ You can't. But you should do monitoring and error
tracking!

@slobodan_ There are many awesome monitoring tools, and a lot
of them are from Israel!* * Epsagon, Lumigo, and others.

@slobodan_ Serverless apps often heavily relies on front end, make
sure you track front end errors too!

@slobodan_ Also, services are smaller and smaller, but integrations require
fine grained permissions.

@slobodan_ There are tools that can help you to improve
your permissions and keep your app secure.* * Protego, Puresec, and others.

@slobodan_

@slobodan_ Summary

@slobodan_ • You can run/test some parts of serverless app
locally, but not everything. • Automated tests are important, but be smart. • Use hexagonal architecture to stay flexible. • Make sure you are tracking errors, unless you want them to scale, too.

@slobodan_ One more thing…

@slobodan_ Serverless Days Belgrade Friday, September 13, 2019 Belgrade Serbia
serverlessbelgrade.com

@slobodan_ And one more…

@slobodan_ Serverless Applications with Node.js Use claudia40 promo code for
40% off serverless.pub/book @slobodan_

Testing Serverless Applications @ Serverless Days Tel Aviv

Testing Serverless Applications @ Serverless Days Tel Aviv

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