A test tool provides a flexible resource for control an of electronic gaming machine (EGM) via a data network. The test tool provides both interactive and automated access to the EGM when the EGM is operated using a special diagnostic BIOS that supports both communication with the test tool over the data network and the ability to set operational variables including random numbers. The test tool can use structured data test scripts, such as XML files, to automate repetitive testing of one or more gaming machines by automating breakpoint setting, variable settings, and comparison of expected results based on game type, paytables, currency, etc.