Software Performance Testing in Virtual Time

We show how traditional unit testing frameworks can be extended to support the simultaneous testing of behaviour and performance, by embedding performance models in mock objects. Because such models are virtual, and therefore execute in virtual time, performance tests can often be performed substantially quicker than when real resources are involved. Performance models also facilitate testing before some or all of a unit»s intended collaborators have been implemented. A key technical challenge is to overcome the impedance mismatch which arises when code that is executing in real time has to communicate with performance models that execute in virtual time. Solutions to this problem naturally facilitate virtual time scaling of both real code and performance models. We also explore potential applications of such time scaling in software performance testing and optimisation.