Abstract: A method and apparatus for substantially reducing the problems associated with prior methods and apparatus for measuring the RF characteristics of electronic circuitry. The method and apparatus allow “in-package” testing of microwave modules, or subassemblies, without the need for additional test fixtures. Preferably, the testing is based on a discontinuous transmission line and at least one waveguide. The discontinuous transmission line electrically isolates two or more modules so that they may be tested individually. The discontinuous transmission line may then be connected using, for example, a ribbon bond. Once the transmission line is connected, the two modules may be capable of communicating with one another. One advantage of the method and apparatus is that the RF characteristics of one or more modules may be determined in their actual operating environment.