A Reduced Test Suite for Protocol Conformance Testing

Abstract

Let M be a finite-state machine, and let S be an implementation of M. The protocol-testing problem is the problem of determining if S is a correct implementation of M. One known method for solving this problem, called the W-method, has the disadvantage that it generates a relatively large test set. In this paper, we describe three new versions of this method. We prove that these versions all have the same fault detection capability as the W-method. In addition, we show that in most cases all three generate a smaller number of tests than the W-method. Specifically, suppose M1 and M2 are finite-state machines having n and m states, respectively, where Ml is a specification (M), Mz is an implementation (S), and m n. In addition, suppose they have input alphabet X, where [formula ommited] let a be the total number of strings in a characterization set for Ml, and let be the total number of strings in a transition couer set for Ml. The W-method will generate a test set consisting of [formula ommited] strings. In contrast, our first algorithm will generate a test set containing at most [formula ommited] strings. For our second algorithm, the number of strings will be [formula ommited], and for the third, [formula ommited], When [formula ommited], all three of our algorithms will produce fewer strings than the W-method. Finally, two of our algorithms make use of a heuristic for minimizing the number of strings in a characterization set. We show that the performance ratio for this heuristic has an upper bound of O(log n). © 1994, ACM. All rights reserved.