A Conformance Relation for Model-Based Testing of PLC

This paper focuses on the execution of conformance testing of PLC with I/O scanning which executes a control code; it is assumed that the test sequence has been built from a finite state machine that represents the specified behavior. It is first shown that the conformance relation which allows to decide whether the implementation conforms to the specification or not must be defined from a sequence of observations, and not from only one observation, to take into account the delays introduced by the I/O scanning. Then, a second conformance relation is proposed to avoid that asynchronous detection of synchronous input changes leads to biased or non-valid verdicts; this new relation is defined from the analysis of concurrent transitions and accepted sequences in the specification model.