A method for testing server machine performance is described. A client-emulating server machine has a collection of live data maps for a plurality of transactions for a chosen computing application. A server is in communication with the workstation. The workstation transmits a processing load, including a plurality of the maps for the plurality of transactions, to the server as it executes the computing load. The server measures one or more performance criteria as it executes the load. The performance criteria can include the average response time for a transaction within a load, and the proportion of server CPU time taken by each transaction of the load. By varying the processing load generated by the workstation and assessing the measured performance criteria, it is possible to determine whether the server has satisfactory capacity.