4.5 Scenarios and Testing

The actual execution of a use case, with real data values, is called a scenario. (A scenario is also sometimes defined as an instance of a use case.) We formally define a scenario in Chapter 15: Domain Verification:

A scenario is the planned execution of a use case with ranges of values for signal parameters, initial states for state machine instances, and ranges of values for attributes of objects, so that there is only path through the model.

A scenario is therefore an excellent way to define a test case, but running the test depends on having values for attributes, states, and parameters. At this stage in a system's development, we can supply values for only one of the three: the parameters.

To define the test cases completely so that they can be executed, we must first build the models. Once we have executable UML models, we can supply values for the attributes and states of the system and use the scenarios as test cases. We take up this topic in Chapter 15: Domain Verification.