Integration Testing

Integration testing examines how individual components behave once combined into a larger structure. A single unit may function flawlessly in isolation, yet unexpected issues can surface the moment data flows between modules. In a reservation system, for example, the payment service must update the booking database correctly so that availability reflects real purchases. Integration tests confirm that such connections operate without conflicts or data loss.

This testing level highlights mismatched expectations across components. A service might send a date in a format another module cannot process, or a database might expect a field that a different subsystem never provides. These subtle inconsistencies often stay hidden until modules communicate directly.