3) Interoperation Flow: The flow here means a series of execution steps which are designed to fulfill the target of interoperability testing. These flows include inputting related data for interoperation interface in every execution step, whose purpose is to implement the interoperation between operating systems via calling interface. Then the test system sets the test verdict according to the output results from interoperation interface. The number of interface in single flow and the coverage of interface in different flows should be considered during design.