Abstract—One of the key concepts of service-oriented computing is dynamic binding which favors on-demand integration of services into a running system. Companies can outsource tasks to external partners by using their services and are able to switch over to alternatives at runtime. However, this flexibility comes at a high cost because it complicates the testing process significantly. The major problem with external services is their restricted usability for testing purposes, due to costs or because policies forbid trial invocations. In this paper we present our approach to solve this issue by generating automatically testbeds which emulate external services. Based on previous work on testbed generation, we have developed a technique for intercepting Web service invocations in Java-based systems, generating emulated replicas at runtime, and redirecting the invocations transparently. We describe the concepts of our approach, its applicability, and limitations.