Smart and efficient ways to test serverless architectures

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smart and e ffi cient way to test serverless architectures

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Yan Cui http://theburningmonk.com @theburningmonk AWS user since 2010

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http://bit.ly/yubl-serverless

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Developer Advocate @ Yan Cui http://theburningmonk.com @theburningmonk

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Independent Consultant advise training delivery Yan Cui http://theburningmonk.com @theburningmonk

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“how do I test serverless?”

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Serverless > Lambda

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“Use Lambda to transform data, not transport data”

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AppSync DynamoDB AppSync DynamoDB Lambda

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Step Functions

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge SNS

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Serverless > Lambda, Serverless > APIs

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Di ff erent services present di ff erent challenges to testing

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Hard Easy

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Hard Easy Lambdalith (e.g. express.js in Lambda)

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Hard Easy Lambdalith (e.g. express.js in Lambda) API Gateway with Lambda

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Hard Easy Lambdalith (e.g. express.js in Lambda) Step Functions with direct integrations Step Functions with timeouts or wait state(s) API Gateway with Lambda

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Hard Easy Lambdalith (e.g. express.js in Lambda) Step Functions with direct integrations Step Functions with timeouts or wait state(s) Event-Driven Architecture API Gateway with Lambda

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https://testserverlessapps.com

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https://testserverlessapps.com Chapter 1: how to test serverless architectures Chapter 2: testing API Gateway APIs Chapter 3: testing AppSync APIs Chapter 4: testing Step Functions Chapter 5: testing Event-Driven Architectures Chapter 6: testing in production

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the RECIPE to TESTING serverless architectures

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#1: “remocal” testing for Lambda functions

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Local testing Runs code locally Can use debugger Change code without deployment FAST FEEDBACK!

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Test against mocks Test against real thing “does it work?” “does it do what I expect?”

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Test against mocks Test against real thing “does it work?” “does it do what I expect?” Expectations/Assumptions are sometimes wrong… Reality!

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Local testing Runs code locally Can use debugger Change code without deployment FAST FEEDBACK! Limited coverage Prone to false positives LOW CONFIDENCE

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Your application consists of more than just your code

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Your application consists of more than just your code Your job is to ensure all of it works

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HIGH CONFIDENCE! Local testing Remote testing Runs code locally Can use debugger Change code without deployment FAST FEEDBACK! Limited coverage Prone to false positives LOW CONFIDENCE Test in the cloud Realistic tests Better coverage

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Local testing Remote testing

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REMOCAL testing Runs code locally, talk to real AWS services Can use debugger Change code without deployment Realistic tests

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Cognito API Gateway AppSync EventBridge

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Cognito API Gateway AppSync EventBridge IAM, event pattern, etc. IAM, URL path, method, etc. IAM, resolver con fi g, resolver template, etc.

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Your application consists of more than just your code Your job is to ensure all of it works

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Auth Cognito AWS_IAM API Key Lambda authorizer Request validation Request transform Integration Lambda Direct service integration Domain logic Integrations Response transform IAM

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Auth Cognito AWS_IAM API Key Lambda authorizer Request validation Request transform Integration Lambda Direct service integration Domain logic Integrations Response transform IAM Unit Test Remocal Test E2E Test E2E Test E2E Test E2E Test E2E Test

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DEMO TIME

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REMOCAL testing Runs code locally, talk to real AWS services Can use debugger Change code without deployment Realistic tests AWS resources need to be provisioned

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#2: Ephemeral environments

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npx sls deploy -s dev-my-feature Step 1: (creates a new “dev-my-feature” environment)

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npx sls deploy -s dev-my-feature Step 1: (creates a new “dev-my-feature” environment) Step 2: Make code changes, iterate, run remocal tests against the “dev-my-feature” environment

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npx sls deploy -s dev-my-feature Step 1: (creates a new “dev-my-feature” environment) Step 2: Make code changes, iterate, run remocal tests against the “dev-my-feature” environment Step 3: Commit code and send PR Step 4: npx sls remove -s dev-my-feature (destroys the ephemeral environment) (CI pipeline runs all tests, etc.)

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Insulated environment for development and testing

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Insulated environment for development and testing (avoids polluting shared dev/test/staging environments with test data)

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No cost overhead with usage-based pricing

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https://theburningmonk.com/2023/02/how-to-handle-serverful-resources-when-using-ephemeral-environments

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environment !== AWS account

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Accounts dev test staging prod test dev staging prod

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Accounts dev test staging prod test dev staging prod dev-yan feature-a feature-b

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Accounts dev test staging prod test dev staging prod dev-yan feature-a feature-b different stacks

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Accounts dev test staging prod test dev staging prod dev-yan feature-a feature-b different CDK apps

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Accounts dev test staging prod test dev staging prod dev-yan feature-a feature-b combination of something

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“How do I make sure resource names don’t clash?”

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#1: Don’t explicit name resources (unless you have to) “How do I make sure resource names don’t clash?”

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#1: Don’t explicit name resources (unless you have to) “How do I make sure resource names don’t clash?” #2: Include environment name in resource names

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remocal testing + ephemeral environments = test Lambda functions with ease BUT…

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Serverless > Lambda

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Step Functions

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{ “provider”: “stripe” }

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{ “provider”: “stripe” }

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{ “provider”: “stripe” } Check for execution result Validate side-effects

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{ “provider”: “stripe” }

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{ “provider”: “stripe” } How to make this step fail/timeout?

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{ “provider”: “stripe” }

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{ “provider”: “stripe” } How to make Stripe return a failed response?

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The further away a state is, the harder it is to test (di ff i cult to direct execution along the desired path)

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What I want to test

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Timeout and Wait states are hard to test

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#3: Step Functions Local

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state machine name

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state name

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state name response name

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state name

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yeah, it’s awkward… but it works and the best we’ve got right now…

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yeah, it’s awkward… but it works and the best we’ve got right now… But mocked responses doesn’t skip time, and can’t throw timeout errors

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What I want to test rewrite the Wait state in local state machine

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DEMO TIME

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Event-Driven Architecture in a nutshell: Something happened Do something

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Event publisher Event consumer EventBridge

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Asynchrony means you don’t know when the event has been processed.

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge

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Hard Easy Lambdalith (e.g. express.js in Lambda) Step Functions with direct integrations Step Functions with timeouts or wait state(s) Event-Driven Architecture API Gateway with Lambda

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests Unit Test Remocal Test

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests Mocks Unit Test

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests Mocks Unit Test

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Test against mocks Test against real thing “does it work?” “does it do what I expect?” Expectations/Assumptions are sometimes wrong… Reality!

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests Remocal Test

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests How to capture what was sent? Remocal Test

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge E2E tests

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge E2E tests How to capture what was sent? How to capture what was sent? How to capture what was sent?

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge E2E tests SNS How to capture what was sent?

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#4: Capture async events/messages

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Lambda EventBridge System under test

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Lambda EventBridge System under test AppSync (subscription)

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Lambda EventBridge Push System under test AppSync (subscription)

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Lambda EventBridge Push Shared infra AppSync (subscription)

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service service service

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge AppSync (subscription)

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Lambda EventBridge Lambda SNS Lambda DynamoDB Lambda DynamoDB SQS DLQ EventBridge Component tests AppSync (subscription) Remocal Test

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DEMO TIME

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#4: Capture async events/messages #3: Step Functions Local #2: Ephemeral environments #1: “remocal” testing for Lambda functions