On Mutating UPPAAL Timed Automata to Assess Robustness of Web Services

We present a model-based mutation technique for testing the robustness of Web service compositions. Specifications of a Web service composition is modeled by UPPAAL Timed Automata and the conformance between the model and the implementation is validated by online model-based testing with the UPPAAL TRON tool. By applying a set of well-defined mutation operators, we generated model mutations. We validate all generate mutants and exclude the invalid ones. The remaining mutants are used for online robustness testing providing invalid test inputs and revealing vulnerabilities of the implementation under test. We experimented our method on a Booking System web service composition. The results show that from a total of 1346 generated mutants, 393 are found suitable for online model-based testing. After running the tests, 40 of the mutants revealed 3 new errors in the implementation. The experiment shows that our approach of mutating specifications is effective in detecting errors that were not revealing in the conventional conformance testing methods.