Feedback Control of the Software Test Process Through Measurements of Software Reliability

A closed-loop feedback control model of the Software Test Process (STP) is described. The model is grounded in the well established theory of Automatic Control. It offers a formal and novel procedure for using product reliability or failure intensity as a basis for closed loop control of the STP. The reliability or the failure intensity of the product is compared against the desired reliability at each checkpoint and the difference fed back to a controller. The controller uses this difference to compute changes necessary in the process parameters to meet the reliability or failure intensity objective at the terminal checkpoint (the deadline). The STP continues beyond a checkpoint with a revised set of parameters. This procedure is repeated at each checkpoint until the termination of the STP. The procedure accounts for the possibility of changes, during testing, in reliability or failure intensity objective, the checkpoints, and the parameters that characterize the STP. The effectiveness of this procedure was studied using commercial data available in the public domain and also from the data generated through simulation. In all cases the use of feedback control produces adequate results allowing the achievement of the objectives.