Testing Serverless Applications

@slobodan_ Meet Alex

@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

@slobodan_

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

@slobodan_

@slobodan_ Meet Slobodan

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

@slobodan_ Running a serverless app locally

@slobodan_ Can you run serverless apps locally?

@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 what about permissions or other services, such as
AWS Cognito or Kinesis?

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

@slobodan_ But, even multiple environments per developer are still cheap
and (relatively) easy to setup

@slobodan_ Can we do better?

@slobodan_ Yes, write tests!

@slobodan_

@slobodan_ Automated testing

@slobodan_ Why do we need to test serverless application?

@slobodan_ Tools for testing

@slobodan_ You can use tools that you are already using

@slobodan_ • Jasmine • Mocha • Jest • any other
popular tool For example, for Node.js you can use:

@slobodan_ What should you 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 to write testable function?

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

@slobodan_ Hexagonal architecture!

@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

@slobodan_

@slobodan_ Unit testing

@slobodan_ Unit testing is the same as for any other
app

@slobodan_ • small units • fully covered with tests •
"mock" adapters

@slobodan_ Integration testing

@slobodan_ Integration tests are more important than ever

@slobodan_ • hexagonal architecture • be smart • test integrations
that you own • or test your code with a different adapter

@slobodan_ How does this look in practice?

@slobodan_

@slobodan_ UI testing

@slobodan_ Serverless is mainly a back end thing, why do
we mention UI tests?

@slobodan_ UI tests are slow and expensive

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

@slobodan_

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

@slobodan_

@slobodan_ CI / CD

@slobodan_ It works the same way as any other app

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

@slobodan_ Popular CI/CD tools

@slobodan_ • Jenkins • Travis CI • Semaphore CI •
AWS CodePipeline • and many more

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

@slobodan_

@slobodan_ Quality Assurance (QA)

@slobodan_ Nothing changes?

@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 test environments was never cheaper

@slobodan_ Bonus: You can promote tested function to production, so
QA tests the same function that will be in production

@slobodan_ One more thing…

@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 (but they are getting easier and easier)

@slobodan_ You should use well tested and mature deployment tool

@slobodan_ Popular deployment tools

@slobodan_ • Serverless Framework • Claudia.js • AWS SAM •
.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_ Monitoring/error-tracking tools

@slobodan_ • Built-in tools (CloudWatch, X-Ray for AWS) • Epsagon
• IOpipe • Lumigo • Thundra • and others

@slobodan_ Serverless apps often heavily relies on front end, in
those cases you need to track front end errors as well

@slobodan_ desole.io

@slobodan_

@slobodan_ Summary

@slobodan_ • you can run/test some parts of serverless app
locally • automated tests are important, but be smart • use hexagonal architecture to stay flexible • use CI/CD for tests and deployment to different stages • QA can test the same function you are deploying to production • use mature and tested deployment tools, and track and analyze errors • serverless helps testers to do their job faster and cheaper

@slobodan_ A few things that I mentioned in this talk:
bit.ly/aws-hexagonal-architecture claudiajs.com desole.io

@slobodan_ vacationtracker.io <shamless-plug> </shamless-plug>

@slobodan_ One more thing…

@slobodan_ First footage of @slobodan_ and @simalexan as AWS Serverless
Heroes Private archive

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

@slobodan_ Thank you!

@slobodan_ Thank you! Diolch i chi!

Testing Serverless Applications - Serverless Da...

Testing Serverless Applications - Serverless Days Cardiff 2019

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