Abstracttest method aims to enable test suite designers to use the most appropriate methods for their circumstances. Most existing methods are end system oriented, rather than relay system concerned. This paper discusses the abstract test methods for relay system testing, introduces the model of the R SUT (relay system under test), gives the conceptual architecture of relay system testing, and proposes several abstract test methods. Finally, some practical experience for testing the relay system, such as IP router,SMTP email server,and Packet Assembly/Disassembly(PAD),is illustrated with the methods presented.These methods could be used for testing ATM switch too.