Model-Based Testing Using System vs. Test Models - What Is the Difference?

We discuss the differences between using system models and test models with respect to the model-based testing process. Although these two terms are usually used interchangeably, very little is known about the distinction between the two. System models describe internal behavior of the system under test while the test models contain the behavior from user´s or environment´s point of view. We describe how these two types of models are obtained and used throughout the model-based testing process and how they are related to each other. The discussion is based on our earlier experiences as well as on two case study examples from the telecommunication domain.