A facility executes on a central computer system and applies a time-varying load to an application program under test (AUT). The facility executes in a multiple number of modes or hierarchical levels as dictated by information provided in its configuration file. An instance of the facility executing at the highest or first-level of the hierarchy is responsible for spawning numerous subordinate or second-level instances of the facility on, for example, remote computer systems. These second-level instances of the facility may spawn additional subordinate or third-level executors on the same or remote computer systems. Ultimately, the lowest-level or leaf instances of the facility are spawned, and these leaf instances of the facility are responsible for launching the client test program instances that are used to test the AUT.