Section: New Results

Asynchronous Testing

In the final year of the TECSTES project, we have extended and completed the co-ioco - based conformance and testing theory that we had developed thus far and published in [21] , in several directions:

• The testing framework now provides a test generation algorithm [21] for concurrent systems specified with true concurrency models, such as Petri nets or networks of automata. The semantic model of computation of such formalisms are labeled event structures, which allow to represent concurrency explicitly.

• Our test generation algorithm based on Petri net unfolding is able to build a complete test suite w.r.t our co-ioco conformance relation [22] . In addition we propose several coverage criteria that allow to select finite prefixes of an unfolding in order to build manageable test suites.

• We propose an extension of the ioco conformance relation, a standard for labeled event structures, named co-ioco, allowing to deal with strong and weak concurrency. We extend the notions of test cases and test execution to labeled event structures, and give a test generation algorithm building a complete test suite for co-ioco. Further, we have introduced and exploited [21] the notions of strong and weak concurrency: strongly concurrent events must be concurrent in the implementation, while weakly concurrent ones may eventually be ordered, leading to refine co-ioco into the wsc-ioco relation accounting for weak and strong concurrency.

• The co-ioco relation assumes a global control and observation of the system under test, which is not usually realistic in the case of physically distributed systems. Such systems can be partially observed at each of their points of control and observation by the sequences of inputs and outputs exchanged with their environment. Unfortunately, in general, global observation cannot be reconstructed from local ones, so global conformance cannot be decided with local tests. We showed in [39] how appending time stamps to the observable actions of the system under test in order to regain global conformance, via vector clock information, from local testing.

• The MOLE - based testing tool TOURS [42] has been developed with the help of intern Konstantinos Athanasiou, jointly supervised by Hernán Ponce de León and Stefan Schwoon of the MExICo team at LSV), and successful experiments have been conducted with a scalable benchmark example (elevator control). The results show clearly how the true-concurrency approach leads to the test case required being not only smaller individually, but also that fewer such test cases are necessary. In addition to the conceptual and analytical enrichment, the results obtained in TECSTES thus also allow to obtain important speedups and reductions in storage space.

Hernán Ponce de León has completed his thesis [40] reporting on the above results, and very successfully defended on Nov. 7, 2014, at ENS Cachan, before the PhD committee consisting of reviewers Rob Hierons and Alex Yakovlev, examiners Thierry Jeron, Remi Morin and Pascal Poizat, and the two supervisors.