Systematic testing for control applications

Software controllers for physical processes are at the core of many safety-critical systems such as avionics, automotive engine control, and process control. Despite their importance, the design and implementation of software controllers remains an art form; dependability is generally poor, and the cost of verifying systems is prohibitive. We illustrate the potential of applying program analysis tools on problems in controller design and implementation by focusing on concolic execution, a technique for systematic testing for software. In particular, we demonstrate how a concolic execution tool can be modified to automatically analyze controller implementations and (a) produce test cases achieving a coverage goal, (b) synthesize ranges for controller variables that can be used to allocate bits in a fixed-point implementation, and (c) verify robustness of an implementation under input uncertainties. We have implemented these algorithms on top of the Splat test generation tool and have carried out preliminary experiments on control software that demonstrates feasibility of the techniques.