Everyone is familiar with testing and test automation. We often use automated unit and integration tests, and usually also test at system level to a lesser extent. However, these methods can reach their limits as soon as they are coupled with external systems. It is necessary to represent interrelated processes that affect your own system from the outside. Imagine a list of requests from several external systems (e.g. from an app, a website and/or IoT devices), which together form a process. At this point, simulators and emulators can help to support both individual and mass tests. In this presentation, we will look at possible scenarios and discuss how they can be used in our own projects.