integration-testing

Integration tests against real databases and brokers use containerized environments to spin up actual services. This approach validates component interactions end-to-end by coordinating real container instances rather than relying on isolated mocks.

Contract testing in a containerized environment verifies routing, middleware, and serialization within service boundaries. It validates inter-service contracts by running end-to-end HTTP tests against real containerized services to ensure components communicate correctly.

Docker is required for Testcontainers-based integration suites because the tests launch real databases, brokers, and services as containers. You also need a test framework like pytest or jest and orchestration scripts to coordinate migrations.

Pytest or jest can be used for end-to-end HTTP testing with containerized services. The integration suite launches real services using Testcontainers, performs HTTP tests, and verifies contracts while the test framework handles assertions and reporting.

Tests with mocked I/O fail to catch integration issues because isolated components do not validate real interactions with databases, brokers, or services. Containerized integration testing provides reproducible environments that reveal routing and serialization failures mocks miss.

Testcontainers may not suit integration testing when Docker is unavailable or when tests require rapid execution without container startup overhead. For simple unit-level component validation, mocked I/O is faster, but it will not verify end-to-end service interactions.