Testing is a necessary step in systems integration. Testing in the context of interenterprise, business-to-business (B2B) integration is more difficult and expensive than intra-enterprise integration. Traditionally, the difficulty is alleviated by conducting the testing in two stages: conformance testing and then interoperability testing. In conformance testing, systems are tested independently against a referenced system. In interoperability testing, they are tested simultaneously against one another. In the traditional approach for testing, these two stages are performed sequentially with little feedback between them. In addition, test results and test traces are left only to human analysis or even discarded if the solution passes the test. This paper proposes an approach where test results and traces from both the conformance and interoperability tests are analyzed for potential interoperability issues; conformance test cases are then derived from the analysis. The result is that more interoperability issues can be resolved in the lower-cost conformance testing mode; consequently, time and cost required for achieving interoperable solutions are reduced.