AWS Infrastructure Integration Testing with Localstack

When verifying logic that uses AWS services like SES or S3, using actual AWS resources can cause problems such as incurred costs, difficulty managing secrets, and impaired independence between tests.

To solve this, Localstack, which simulates the AWS API, was adopted. Localstack runs as a Docker container, enabling the construction of an independent test environment in both local and CI environments.

For the test execution method, Testcontainers and Docker Compose were compared and reviewed.

• Testcontainers: Manages the container lifecycle for each test, guaranteeing independence, but individual test speed is slow and load can occur when running a large number of containers.
• Docker Compose: A single Localstack instance is run in advance, making test execution fast and management easy, so this approach was ultimately adopted.

For efficient testing, an initialization script (/docker-entrypoint-initaws.d) was used to automate preliminary tasks such as creating S3 buckets and verifying SES emails.