This paper describes cidl, a tool that helps CORBA developers test liveness properties in distributed systems. Whereas examining initial states and outcomes can test sequential systems, distributed systems frequently exhibit reactive behavior that occurs over time. Liveness properties capture such behavior. Testing liveness, however, presents a significant challenge because liveness violations can never be detected during a finite execution.We present a testing technology for CORBA-based distributed systems. We define an extension to CORBA IDL for specifying a fundamental liveness property: transient. The cidl tool uses this extension to generate a testing harness for tracking liveness. We describe how to use cidl for testing and debugging and present a preliminary experience report.