A testing system for a reverse client-server system management program comprises a server connected to one or more recipient devices and emulating devices through one or more repeaters. The recipient devices act as targets for the management program and the emulating devices emulate one or more of the recipient devices, to enable an assessment of the scalability of the management program to a large number of targets. The repeaters direct management requests from the server to the target devices depending on the configuration of the hook and/or the nature of the operation requested by the management request. The recipient devices and emulating devices execute the required system management operation on receipt of a management request from the server (via the repeaters). The recipient devices and emulating devices generate and transmit a report detailing the outcome of the system management operation.