Tech debt: Audit unit tests and replace external dependencies by mocks

[phipag]

Why is this needed?

Currently, some unit tests such as powertools-idempotency-dynamodb depend on running a local server for mocking AWS resources.

This violates the principle that unit tests should run in a self-contained way.

Example which should be avoided:

powertools-lambda-java/powertools-idempotency/powertools-idempotency-dynamodb/src/test/java/software/amazon/lambda/powertools/idempotency/persistence/dynamodb/DynamoDBConfig.java

Lines 50 to 55 in 7b18029

	dynamoProxy = ServerRunner.createServerFromCommandLineArgs(new String[] {
	"-inMemory",
	"-port",
	Integer.toString(port)
	});
	dynamoProxy.start();

This starts a DynamoDB mock server on localhost.

Which area does this relate to?

Tests

Suggestion

This issues suggests to:

1. Audit all unit tests for external dependencies
2. Replace external dependencies by self-contained mocking
3. Add a test scenario in the end2end tests to cover the use-case using real infrastructure in real AWS accounts

Acknowledgment

• This request meets Powertools for AWS Lambda (Python) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Python, TypeScript, and .NET

[Pratapchandradeo]

Hi, @phipag can you assign this one to me ?

[phipag]

Hey @Pratapchandradeo,

yes. Happy to do this. Before opening a PR let's agree on a plan here. I would be happy to see your suggestions and audit for the different modules.

[Pratapchandradeo]

I’ll do a quick audit across modules to identify any “unit tests” that rely on external services (localhost servers, DynamoDB Local, LocalStack/Testcontainers, etc.) and post a short list here: module → test → dependency → recommendation (mock in unit vs move to e2e).

Then we can agree on priorities, and I’ll start with powertools-idempotency-dynamodb by replacing the local server usage with mocks, and add a separate e2e scenario against real AWS to cover the real behavior.

Quick confirm: should LocalStack/Testcontainers also be removed from unit tests (and kept only for e2e/integration)?

[phipag]

Sounds good @Pratapchandradeo.

We don't use any localstack or testcontainers today.

[Pratapchandradeo]

Thanks for confirming. In that case, I’ll focus the audit specifically on unit tests that start embedded/local servers or use localhost endpoint overrides the DynamoDB local mock server in powertools-idempotency-dynamodb, since we’re not using LocalStack/Testcontainers. I’ll post a module-by-module list of findings and proposed mock-based replacements here before opening the first PR.