Abstract: A mainframe testing framework is provided that permits users to execute and store API and/or service test logic for mainframe APIs or services on-platform and/or of platform, and to access the mainframe system to execute the test logic on an as-needed basis. An API/service to be tested is identified and a mainframe address space is created that hosts the API/service. A command syntax, a test command and a corresponding response are received by the mainframe address space. An automated test (stored on- or off-platform) is received that invokes execution of the test command. It then is determined if the corresponding response is received in response to execution of the test command.