Integration Testing Explained

Verify that your components, services, and infrastructure work together correctly by testing real interactions rather than mocked interfaces.

Integration Testing

Integration testing verifies that multiple components, modules, or services work correctly together, testing the interactions and data flow between integrated parts of a system.

Explanation

While unit tests verify individual components in isolation, integration tests verify that those components work together correctly. They test the "seams" between modules: database queries against a real database, API calls between services, message queue producers and consumers, and authentication flows across systems. Integration tests are slower than unit tests because they involve real infrastructure (databases, message brokers, external services), but they catch an entire class of bugs that unit tests miss: serialization errors, schema mismatches, network timeouts, transaction isolation issues, and configuration problems. Common approaches include testing API endpoints against a running server with a test database, testing service interactions with containerized dependencies (using Docker Compose or Testcontainers), and contract testing where services verify they conform to agreed-upon API contracts.

Bookuvai Implementation

Bookuvai runs integration tests in CI/CD pipelines using Testcontainers to spin up real databases, Redis instances, and message brokers. Every API endpoint is tested against actual infrastructure, and service-to-service contracts are verified automatically on every pull request.

Key Facts

  • Tests interactions between multiple components or services
  • Uses real infrastructure (databases, queues) rather than mocks
  • Catches serialization errors, schema mismatches, and configuration bugs
  • Slower than unit tests but catches integration-specific failures
  • Testcontainers and Docker Compose provide isolated test environments

Related Terms

Frequently Asked Questions

How many integration tests should I write?
Follow the testing pyramid: fewer integration tests than unit tests, but enough to cover critical paths. Focus on database interactions, API contracts, authentication flows, and payment processing — areas where integration failures cause the most damage.
Should integration tests use a real database?
Yes. Testing against an in-memory substitute (like H2 instead of PostgreSQL) misses database-specific behavior: JSON operators, full-text search, transaction isolation, and migration compatibility. Use Testcontainers to run the same database version as production.
What is contract testing?
Contract testing verifies that a service conforms to the API contract expected by its consumers. Tools like Pact let consumers define expected requests and responses, and producers verify they satisfy those expectations. This catches breaking changes before deployment.