Testing with Functions as Specifications

In this paper we show that mathematical functions and logi- cal expressions can very well be used as, partial, specications. Reactive systems can be modelled by powerful extended state transition systems, that can be nondeterministic and can handle parameterized and in- nite types for the inputs, outputs and states. These specications can very concisely and directly be stated in a modern functional program- ming language. The test tool Gast is able to generate test data based on these specications, execute the associated tests, and make a verdict fully automatically. Test data can be generated fully automatically, but can also be tailored in various high level ways, if that is desired. Advantages of this approach are that one species properties instead of instances of these properties, test data are automatically derived instead of manually, the tests performed are always up to date with the current specication, and testing is automatic (and hence fast and accurate).