The minimum length test sequence generation method proposed previously (1988) for conformance testing of a protocol uses Unique Input Sequences (UIS) for state identification. This method, called the U-method, requires that the test graph, a graph derived from the protocol, be connected. This requirement also needs to be satisfied in the case of the MU-method, which assumes that the multiple UISs are available for each state. Thus, the U-method and the MU-method may not provide minimum length test sequences in cases where the test graph is not connected. Nevertheless, these methods generate minimum length test sequences with high fault coverage whenever the test graph is connected. This raises an important problem: Does there exist an assignment of UISs to the transitions such that the resulting test graph is connected? In this paper, we formulate this problem as a maximum cardinality two matroid intersection problem and discuss an efficient algorithmic solution. We also point out the role of the work in the minimum length test sequence generation problem.

A number of test sequence generation methods proposed for protocols represented as extended finite state machines (EFSMs) use state identification sequences for checking the states. However, neither a formal definition nor a method of computation of these sequences for an EFSM state is known. We define a new type of state identification sequence, called context independent unique sequence (CIUS) and present an algorithm for computing it. A unified method based on CIUSes is developed for automatically generating executable test cases for both control flow and data flow aspects of an EFSM. In control flow testing, CIUSes are very useful in confirming the tail state of the transitions. In data flow testing, CIUSes improve the observability of the test cases for the def-use associations of different variables used in the EFSM. Unlike general state identification sequences, the use of CIUSes does not increase the complexity of the already intractable feasibility problem in the test case generation.