System test scenarios use external systems in the same way as in production. However, similar to mock objects in unit and component tests, system tests simulate and mock away external systems. In this way, potential issues that the application isn't responsible for are eliminated. System tests run in dedicated environments, for example, provided by container orchestration frameworks. The test object is the sole application, deployed, executed and configured in the same way as in production.

Simulated external systems are configured to provide the expected behavior once accessed by the application. Similar to a mock object, they verify correct communication depending on the use case.

For the majority of use cases, used databases would not be mocked away. The test scenario can manage and populate database contents as part of the test life cycle, if required. If the database system contains a lot of concerns external to the application, for example containing a lot of database code or representing a search engine, it may make sense to mock and simulate this behavior.

Container orchestration strongly supports these efforts by abstracting systems as services. Pod images can be replaced by other implementations without affecting the tested application. The mocked services can be accessed and configured from within the running system test, defining behavior and external test data.

The dotted line illustrates the control and verification of the mocked system as part of the test scenario. The running application will use the external service as usual, with the difference that this service is in fact, backed by a mock.