Integration Tests

“Integration test” is widely used but inconsistently defined. On this site, integration tests are tests that involve real external dependencies - actual databases, live downstream services, real message brokers, or third-party APIs. They are non-deterministic because those dependencies introduce timing, state, and availability factors outside the test’s control.

Integration tests serve a specific role in the test architecture: they validate that the test doubles used in your contract tests still match reality. Without integration tests, contract test doubles can silently drift from the real behavior of the systems they simulate - giving false confidence.

Because integration tests depend on live systems, they run post-deployment or on a schedule - never as a pre-merge gate. Failures trigger review or rollback decisions, not build failures.

For tests that validate interface boundaries using test doubles (deterministic), see Contract Tests.

For full-system browser tests and multi-service smoke tests, see End-to-End Tests.