This volume contains the proceedings of the 16th IFIP TC6/WG6.1 Inter- tional Conference on Testing of Communicating Systems (TestCom 2004). This conference was held at St Anne s College, Oxford, UK, from March 17 to March 19, 2004. TestCom 2004 was the sixteenth in a series of IFIP-sponsored events that started in 1988. The previous events were held in Vancouver, Canada (1988); B- lin, Germany (1989); McLean, USA (1990); Leidschendam, Netherlands (1991); Montreal, Canada (1992); Pau, France (1993); Tokyo, Japan (1994); Evry, France (1995); Darmstadt, Germany (1996); Cheju Island, Korea (1997); Tomsk, R- sia (1998); Budapest, Hungary (1999); Ottawa, Canada (2000); Berlin, Germany (2002); and Sophia Antipolis, France (2003). TestCom was not held in 2001 since at this point the conference moved from autumn to spring. TestCom 2004 was organized by Brunel University, UK and LSR-IMAG, France and was sponsored by IFIP. Support was also provided by the Engineering and Physical Sciences Research Council (EPSRC). We are grateful to the keynote speaker, Prof. Sir Tony Hoare, FRS, and our invited speakers for agreeing to address TestCom 2004.

Inhalt
Implementation of an Open Source Toolset for CCM Components and Systems Testing.- A Multi-service and Multi-protocol Validation Platform Experimentation Results.- From Design to Test with UML.- BCMP Performance Test with TTCN-3 Mobile Node Emulator.- FSM Based Interoperability Testing Methods for Multi Stimuli Model.- On Testing Partially Specified IOTS through Lossless Queues.- Testing Multi Input/Output Transition System with All-Observer.- Soip Over Satellite Testing TIM Experience.- Generation of Optimized Testsuites for UML Statecharts with Time.- Communication Patterns for Expressing Real-Time Requirements Using MSC and Their Application to Testing.- From Safety Verification to Safety Testing.- Derivation of Abstract Protocol Type Definitions for the Conformance Testing of Text-Based Protocols.- Mutation Testing Applied to Validate SDL Specifications.- Execution of External Applications using TTCN-3.