The complex interactions appearing in service-oriented computing make coordination a key concern in service-oriented systems. In this paper, we present a fault-based method to generate test cases for component connectors from specifications. For connectors, faults are caused by possible errors during the development process, such as wrongly used channels, missing or redundant subcircuits, or circuits with wrongly constructed topology. We give test cases and connectors a unifying formal semantics by using the notion of design, and generate test cases by solving constraints obtained from the specification and faulty connectors.