Using Imprecise Test Oracles Modelled by FSM

Test oracles are usually used to evaluate the behaviors of systems under test to reveal faults. In a typical conformance testing scenario, a test oracle is a deterministic finite state machine (FSM). However, uncertainty occurring in the design of an oracle may result in a set of potential candidate oracles which can compactly be represented by a nondeterministic FSM thus modelling an imprecise test oracle. In the context of testing deterministic systems, such an oracle should ideally be reduced to a precise, i.e., deterministic oracle. We elaborate two scenarios for dealing with imprecise test oracles that involve a domain expert playing the role of an "ultimate" oracle. In the first scenario, the expert chooses a right oracle by inspecting the generated tests differentiating all potential precise oracles which can be derived from a given imprecise one. In the second scenario, the expert evaluates tests one by one while they are generated, and the imprecise oracle is iteratively reduced until a single precise oracle remains, if at all.