Abstract. We present experiences from a case study where a model-based approach to black-box testing is applied to verify that a Wireless Application Protocol (WAP) gateway conforms to its specification. The WAP gateway is developed by Ericsson and used in mobile telephone networks to connect mobile phones with the Internet. We focus on testing the software implementing the session (WSP) and transaction (WTP) layers of the WAP protocol. These layers, and their surrounding environment, are described as a network of timed automata. To model the many sequence numbers (from a large domain) used in the protointroduce an abstraction technique. We believe the suggested abstraction technique will prove useful to model and analyse other similar protocols with sequence numbers, in particular in the context of model-based testing. A complete test bed is presented, which includes generation and execution of test cases. It takes as input a model and a coverage criterion expressed as an observer, an...