Testability of a Communicating System Through an Environment

Testing of a component embedded in a whole system is addressed. The component is not as easy to check as when taken in isolation. The notion of conformance, as introduced by E. Brinksma and G. Scollo, is extended to formalize testing through an environment that does not allow some non conforming implementations to be discarded. A method enabling embedded systems testability to be characterized is proposed. It is based on the refusal graph whose arcs are labeled by events and nodes by subsets of events. An approach is presented to identify erroneous implementations. In particular, the least erroneous implementations discarded by testing through environment are defined and computed.