A system for testing certain attributes (i.e., performance and usability) of an interactive system program. A memory device stores data representative of interactive commands generated by a user. A device is also provided for executing an emulator overlay connected to the memory device for receiving data therefrom and modifying it in subsequent transmission. The emulator overlay has a time measuring device associated with it for determining performance of an interactive system program. A device is also provided for storing and executing an interactive system program connected to the emulator overlay. Finally, another memory device is provided for storing the data representative of system program performance. The system is capable of capturing human factors data, including screen images and associated keystrokes entered during a user session a user session, measuring time intervals between the screen images and keystrokes, and providing such data to a system analyst to determine usability of host computer resident software.