Communication Protocols Testability Improvement by Narrow Input/Output (NIO) Sequences

– Communication protocol conformance testing has become more complex as protocols have grown larger. The study of design for testability (DFT) is a research area to help overcoming the ever increasing complexity of testing distributed systems. In the previous research, we introduced a new metric for testability of communication protocols, demonstrated the usefulness of the metric for identifying faults that are more difficult to detect, and also presented the approach for improved testability without modifying the protocol structure by means of unique input/output (UIO) sequences. Since a UIO sequence may not exist for every state of some protocol specification finite state machines (FSMs), in this paper, we extend UIO sequence to a new general concept called narrow input/output (NIO) sequence. We demonstrate the effectiveness of NIO sequence application on the improvement of protocol testability.