Testing Serverless Applications - AWS Community Days Sofia

Building serverless applications with AWS Lambda sounds exciting, but how does serverless change how we should approach testing? This talk explains the differences with testing serverless applications, what are the risks and how does serverless change integration and unit testing.

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Aleksandar is an AWS Serverless Hero and an experienced senior software engineer at ScienceExchange, coauthor of “Serverless Applications with Node.js” book, published by Manning Publications. He is based in Belgrade and co-organizer of JS Belgrade, Map Meetup Belgrade and Serverless Belgrade. Contributor to AWS SAM, AWS Lambda Builders and many other open source libraries.

Transcript

1. simalexan Meet Slobodan
2. simalexan
3. simalexan
4. simalexan Build with serverless! Its me!
5. simalexan No server management / ops Scales per use Autofailover Don’t pay 
 for idle
6. simalexan Business is more profitable Faster delivery
7. simalexan Code needs to run on servers! Serverless? That’s not the point! You’re an idiot
8. simalexan It is serverless, 
 the same way WIFI is wireless. Gojko Adzic
9. simalexan
10. simalexan Ok, lets try…
11. simalexan AWS Lambda DynamoDB API Gateway AWS S3 To learn…
12. simalexan …the way it has changed…
13. simalexan to build…
14. simalexan …a functioning product
15. simalexan Accidents do happen Something will break…
16. simalexan
17. simalexan …the business suffers
18. simalexan How do I prevent 
 this? You test!
19. simalexan We don’t have time to test! The you will find 
 time to fix!
20. simalexan Ok, how do I test a serverless app?
21. simalexan Testing Serverless Applications
22. simalexan Aleksandar Simovic Senior Software Engineer @ ScienceExchange AWS Serverless Hero coauthor of “Serverless Applications with Node.js” book AWS SAM & Lambda Builders Contributor
23. simalexan Why do you test?
24. simalexan • “Industry standard”. • “90% test coverage is required.” • “Code compliance”. • “You need to ensure that the code works”. The Usual replies
25. simalexan • “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
26. simalexan All (somewhat) 
 valid responses
27. simalexan The purpose of Testing is to find and prevent 
 defects.
28. simalexan • John Null • E Lee • GoVeg.com But Testing only to find or prevent
 defects is not enough
29. simalexan
30. simalexan One of the purposes of testing is to Reduce Risk
31. simalexan What are these risks 
 when building serverless applications?
32. simalexan First, the way we build 
 applications has changed with serverless
33. simalexan
34. simalexan Its risks…
35. simalexan • configuration risks • technical workflow risks • business logic risks • integration risks
36. simalexan Configuration risks Receiving events from the correct API? Access rights? Saving to correct bucket?
37. simalexan Technical workflow risks Handling success / error workflow responses Are we using the incoming events
 correctly? Workflow risks
38. simalexan 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?
39. simalexan Integration risks Are our AppSync GraphQL objects properly set in DynamoDB? Are we reading AND
 writing events from API Gateway to S3 correctly?
40. simalexan How do we address those risks
41. simalexan Good Architecture
42. simalexan What is a good architecture for serverless?
43. simalexan
44. simalexan Hexagonal Architecture
45. simalexan 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.
46. simalexan Boooring! 
 Show me an example
47. simalexan 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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53. simalexan Separate interface risk from your Business logic risk
54. simalexan In code..
55. simalexan 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; }
56. simalexan 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(); } };
57. simalexan What do I test in a serverless app?
58. simalexan What do you test in a traditional app?
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60. simalexan What is different in a serverless app?
61. simalexan Managed (and cheaper) infrastructure,
 many smaller business logic pieces
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63. simalexan Even though with serverless your infrastructure is managed
64. simalexan That doesn’t mean your code is managed as well!
65. simalexan Integration tests are cheaper, but also more important, because a common serverless app is split into many small pieces
66. simalexan Testing your code and your integrations is now more important than before!
67. simalexan I know the 
 “Why”, “risks”, “What”… But now I need the “How”?
68. simalexan How to test serverless 
 applications
69. simalexan Just show me how in practice. Wait! 
 Stop using long words…
70. simalexan First, the tools!
71. simalexan Tools
72. simalexan • Jest • Jasmine • Mocha • Cypress • any other popular tool For example, for Node.js you can use:
73. simalexan Testing is very important on all levels both unit, integrated and end-to-end-testing.
74. simalexan Unit and integration tests!
75. simalexan
76. simalexan Sample unit test code
77. simalexan 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'); }); }); });
78. simalexan • hexagonal architecture • be smart • test integrations that you own • or test your code with a different adapter
79. simalexan If you test and properly design using Hexagonal architecture you’re even out of “vendor lock-in”.
80. simalexan UI testing
81. simalexan Benefits of serverless are cheap infrastructure and easy fast parallelization.
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83. simalexan What about CI/CD?
84. simalexan It works the same way as it did
 with any other app
85. simalexan Use your favorite deployment tool from CI to deploy your serverless app
86. simalexan • Jenkins • Travis CI • AWS CodePipeline • Semaphore CI • CircleCI • and many more
87. simalexan Testing environments? And what about…
88. simalexan Having test environments was never cheaper
89. simalexan Automate deployment from git branches to different stages (ie. production, dev, staging, qa)
90. simalexan Testing slows you down! You’re making it sound too easy…
91. simalexan Actually…
92. simalexan Testing your serverless apps quickens your software delivery even more.
93. simalexan Real life example @ ScienceExchange
94. simalexan Hexagonal Architecture 3 months > 2 weeks Unit / Integration testing + = Going serverless + $40,000 > $10
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97. simalexan • 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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99. simalexan serverless.pub/book “Serverless Applications with Node.js" @simalexan claudia40 40% off Thank you!