Devnexus 2025 - Cloud Integration Testing Made Easy for Your Java Apps

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Cloud Integration Testing Made Easy for Your Java Apps Atlanta March 5th 2025 localstack.cloud

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Anca Ghenade - Developer Advocate - [email protected] @tinyg210

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Testing…

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Some things cannot just easily be tested…

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I was gonna show you my research on landing gear sensors…

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So what’s the ﬁrst thing we take away from this? Integration testing is important.

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And second: it must also be realistic.

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But how realistic?

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The truth is we’ve gotten very used to being “fake”. ● Test data → a clean database on every test run. We get green tests with migration problems. ● Selenium → a fake user, using a mouse and keyboard, over and over again. We assume it’s realistic. ● Stamina → the runtime is always fresh for tests. What about subtle memory leaks? ● Scaling → tests run against a single process web server. Reality: a multi-thread environment.

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Sometimes you have no choice.

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WE INTERRUPT THE REGULAR SCHEDULED PRESENTATION TO BRING YOU THIS IMPORTANT STORY TIME

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So my inspirations for this talk were our Code Cop and Justin Searls and his SCNA 2012 talk: To Mock or Not To Mock.

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How do we test applications with dependencies in the cloud?

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We want to keep it as real as possible when we’re testing our AWS-powered applications and the interaction between various components.

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The reality: (of using a real cloud environment)

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Your painful checklist for everything to consider: ● AWS Account: Ensure access to a test AWS account. ● Separate Test Env: Use a dedicated AWS environment. ● Data Isolation: Keep test data separate from production. ● Service Isolation: Use separate accounts or tagging to avoid conﬂicts. ● Cleanup: Ensure resources are cleaned up post-testing. ● CI Integration: Run tests automatically in CI/CD pipelines. ● IAM Permissions: Ensure test users/roles have the necessary permissions. ● Logging & Monitoring: Enable CloudWatch logs and metrics for debugging test failures. ● Secrets Management: Store and manage test credentials securely (e.g., AWS Secrets Manager, Parameter Store). ● Cost Management: Track and limit test resource usage to avoid unexpected costs. ● Test Parallelization: Ensure tests can run concurrently without conﬂicts. ● State Management: Handle persistent vs. ephemeral resources carefully.

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So things are kind of… complicated. 󰤆

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When it comes to testing, here are some common practices that we’re all guilty of. (At one point in our lives)

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The “let’s prove it works”

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Focus: ● You do some quick end-to-end and integration testing. ● Mocking only the necessities.

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The “mocking the boundaries”

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Focus: ● Mocking remote systems. ● Mostly unit and end-to-end testing. ● Reuse mocks and get tangled when anything changes.

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Circling back to reality… reality is expensive, so we also want to test on a budget.

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Sure mocks are cheap, but you might end up paying a little diﬀerently.

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Mocking carries the risk of not getting updated and if we mock everything, aren’t we just making sure that the mocks work as expected?

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How can we bring the ease and speed of unit tests into our integration tests?

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What is LocalStack and how can it help you? A fully functional local cloud stack that was born out of these exact concerns.

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● Enables a highly eﬃcient dev & test loop for cloud apps ● Ships as a container image, easy to install and start up ● Support for 100+ services (and growing): ○ compute (Lambda, ECS, EKS) ○ various databases (DynamoDB, RDS) ○ messaging (SQS, Kinesis, MSK) ○ some sophisticated/exotic APIs (Athena, Glue) ● CI integrations & advanced collaboration features ● Branching out into other areas: Chaos Engineering, IAM Security Testing, Cloud Ephemeral Environments, 3rd Party Extensions, etc

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How much of your system you can test Cloud emulation Staging environments Real AWS Mocking So how much reality can we have in cloud application testing? 3 4 Service emulation 2 1

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I’ll show you some stuff

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Using Spring Proﬁles…

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Scenario 1 (Production) Scenario 2 (Development)

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Scenario 1 Scenario 2

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Scenario 1 Scenario 2

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What about those integration tests?

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What approach do we use for testing our apps?

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1. The “my app changes frequently” example

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Testing your application workﬂows

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https://github.com/tinyg210/sf-java-meetup-demo

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And your app runs against LocalStack.

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2. The “my app is pretty much ready” example Source: https://github.com/tinyg210/stack-bytes-apigw-lambda-s3 Folder: github-actions-testcontainers

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Test successful POST Test successful GET Test fails validation on incorrect values Test 404 on wrong param

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Your tests will revolve around an HTTP client

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And your app runs inside LocalStack.

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Tips and Tricks Dump

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There are several ways to provision your infrastructure for testing.

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1. You do everything yourself. Programmatically with the AWS SDKs. (example: https://github.com/tinyg210/testcontainers-shipment-list-demo)

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2. Use init hooks to create your AWS resources.

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a. AWS CLI scripts via init hooks (example: https://github.com/tinyg210/stack-bytes-apigw-lambda-s3)

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b. Terraform conﬁguration ﬁles via init hooks.

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3. Use LocalStack Cloud Pods

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Locally…

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There’s a catch: you need to use the same creation major version

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Download on the ﬂy… And see it in the webapp: https://app.localstack.cloud/pods

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4. Use a mix of all of the above. 󰤆 ● spin up only desired services at startup ● manage other resources via SDK clients

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Now how do you interact with the container?

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Did I mention the SDKs?

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Or you can use AWS CLI commands.

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What about testing in CI?

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Your local tests…

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In CI…

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Some More Tips and Tricks

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Use a waiter to make sure your Lambdas are in state ACTIVE and not just created.

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Source: https://aws.amazon.com/blogs/compute/coming-soon-expansion-of-aws-lambda-states-to-all-functions/

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Wait for LocalStack logs to tell you when to start, so that your instance is in the right state before the tests are allowed to start.

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Streaming container output to an SLF4J logger.

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Lastly, shutting down your Lambda containers ﬁnally work!

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Before

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This is just me debugging btw.

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Thank you, Eddu, for that workaround! 󰚦 󰚦 󰗨

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After

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Make use of all the configuration flags: https://docs.localstack.cloud/references/ configuration/

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Thank You!