Distinguishing Sequences for Distributed Testing: Preset Distinguishing Sequences
There has been long-standing interest in automatically generating test sequences from a finite state machine (FSM) and more recently this has been extended to the case where there are multiple physically distributed testers and so we are testing from a multi-port FSM. This paper explores the problem of generating a controllable preset distinguishing sequence (PDS) from a multi-port FSM, motivated by the fact that many FSM-based test generation algorithms use PDSs. We prove that it is generally undecidable whether a multi-port FSM has a controllable PDS but provide a class of multi-port FSMs for which the problem is decidable. We also consider the important case where there is an upper bound ℓ on the length of PDSs of interest, proving that controllable PDS existence is PSPACE-hard and in EXPSPACE. In practice the upper bound ℓ is likely to be a polynomial in terms of the size of the multi-port FSM and in this case controllable PDS existence is NP-Complete.