integration-testing

Integration testing validates end-to-end interactions across APIs, databases, and microservices by combining API testing with database verification. Use containerized environments like Testcontainers or Docker Compose to spin up real database instances, then write tests that exercise API endpoints and verify database state changes in isolation.

Containerized integration testing isolates each microservice's test environment using Docker Compose or Testcontainers, eliminating test dependencies and flakiness. This approach lets you spin up databases, mock services, and dependent components on demand, run tests in parallel, and tear down cleanly after each test suite.

Contract testing using Pact-based frameworks verifies that services honor their communication contracts without requiring full end-to-end integration. It generates contracts from consumer expectations, validates providers against those contracts, and catches breaking changes early in CI before deployment.

Integration testing with real containerized databases lets you apply migrations, verify schema correctness, and test data transformations in an isolated environment. Testcontainers automates database setup, runs migrations against the test instance, and validates that your application handles schema versions correctly.

API mocking within integration tests lets you control external service behavior, simulate error scenarios, and avoid test flakiness from real external dependencies. Combine mocking for unreliable or third-party services with real containerized databases and internal service instances for comprehensive integration coverage.

Contract testing validates bilateral agreements between services using pacts; integration testing validates actual end-to-end workflows across multiple components. Contract testing runs faster in CI, catches incompatibilities early, while integration testing verifies complete system behavior under realistic conditions.