A formal yet user-friendly test description language could increase the possibilities for automation in the testing phase while at the same time gaining widespread acceptance Scenario languages are currently one of the most popular formats for describing interactions between possibly distributed components The question of giving a solid formal basis to scenario languages such as MSC has also received a lot of attention In this article we discuss using one of the most widely-known scenario languages UML sequence diagrams as the basis for a formal test description language for use in the distributed system context .