Abstract: In a diagnostic application, a plurality of independent test modules are executed in a multi-tasking fashion. The diagnostic application is modular with a front end module issuing commands to lower level modules. A lower level test dispatcher module receives information from the plurality of test modules pertaining to test parameters, including whether the test module is multitaskable. A test definition tool is provided to visually develop test scripts by moving icons from one list to another. The output of the test definition tool is a scripting language readable by the diagnostic application.