Abderrazak Ghedamsi

Test selection based on finite state models

A method for the selection of appropriate test case, an important issue for conformance testing of protocol implementations as well as software engineering, is presented. Called the partial W-method, it is shown to have general applicability, full fault-detection power, and yields shorter test suites than the W-method. Various other issues that have an impact on the selection of a suitable test suite including the consideration of interaction parameters, various test architectures for protocol testing and the fact that many specifications do not satisfy the assumptions made by most test selection methods (such as complete definition, a correctly implemented reset function, a limited number of states in the implementation, and determinism), are discussed. >

Test generation with respect to distributed interfaces

Abstract In the area of testing communication systems, the interfaces between systems to be tested and their testers have great impact on test generation and fault detectability. Several types of such interfaces have been standardized by the International Standardization Organization (ISO). A general distributed test architecture, containing distributed interfaces, has been presented in the literature for testing distributed systems based on the Open Distributing Processing (ODP) Basic Reference Model (BRM), which is a generalized version of ISO distributed test architecture. We study in this paper the issue of test selection with respect to such a test architecture. In particular, we consider communication systems that can be modeled by finite state machines with several distributed interfaces, called ports. A test generation method is developed for generating test sequences for such finite state machines, which is based on the idea of synchronizable test sequences. We then apply this method to generate test sequences for a so-called quorum protocol. Starting from the initial effort by Sarikaya, a certain amount of work has been done for generating test sequences for finite state machines with respect to the ISO distributed test architecture, all based on the idea of modifying existing test generation methods to generate synchronizable test sequences. However, none studies the fault coverage provided by their methods. We investigate the issue of fault coverage and point out a fact that the methods given in the literature for the distributed test architecture cannot ensure the same fault coverage as the corresponding original testing methods. We also study the limitation of fault detectability in the distributed test architecture.

Test result analysis and diagnostics for finite state machines

An algorithm that localizes the faulty transition in a deterministic finite state machine (FSM) once the fault has been detected is presented. The diagnostic algorithm generates, if necessary, additional diagnostic test cases which depend on the observed symptom and which permit the location of the detected fault. The algorithm guarantees the diagnosis of any single fault in an FSM. An application example, explaining the functioning of the algorithm, is provided.<<ETX>>

Multiple fault diagnosis for finite state machines

The authors propose a generalized diagnostic algorithm for the case where more than one fault (output and/or transfer) may be present in the transitions of a system represented by a deterministic finite state machine (FSM). If existing faults are detected, this algorithm permits the generation of a minimal set of diagnoses, each of which is formed by a set of transitions (with specific types of faults) suspected of being faulty. The occurrence in an implementation of all the faults of a given diagnosis allows the explanation of all observed implementation outputs. The algorithm guarantees the correct diagnosis of certain configurations of faults (output and/or transfer) in an implementation, which are characterized by a certain type of independence of the different faults. The authors also propose an approach for selecting additional test cases, which allows the reduction of the number of possible diagnoses. A simple example is used to demonstrate the different steps of the algorithm.<<ETX>>

Multiple fault diagnostics for communicating nondeterministic finite state machines

During the last decade, different methods were developed to produce optimized test sequences for detecting faults in, communication protocol implementations. However, the application of these methods gives only limited information about the location of detected faults. We propose a complementary step, which localizes the faults, once detected. It consists of a generalized diagnostic algorithm for the case where more than one fault may be present in the transitions of a system represented by communicating nondeterministic finite state machines, if existing faults are detected, this algorithm permits the generation of a minimal set of diagnoses, each of which is formed by a set of transitions suspected of being faulty. A simple example is used to demonstrate the functioning of the proposed diagnostic algorithm. The complexity of each step in the algorithm are calculated.

Diagnostic tests for communicating finite state machines

The authors propose a diagnostic algorithm for the case where a protocol specification is given in the form of communicating finite state machines (CFSMs). Such an algorithm localizes the faulty transition in the protocol implementation once the fault has been detected. It generates, if necessary, additional diagnostic tests, which depend on the observed symptoms and which permit the location of the detected fault. The algorithm guarantees the correct diagnosis of any single fault in CFSMs. A simple example is used to demonstrate the different steps of the proposed diagnostic algorithm.<<ETX>>

Diagnosis of single transition faults in communicating finite state machines

The authors propose a generalized diagnostic algorithm for the case where more than one fault (output or transfer) may be present in one of the transitions of a deterministic system represented by a set of communicating finite state machines (CFSMs). Such an algorithm localizes the faulty transition in the distributed system once the fault has been detected. It generates, if necessary, additional diagnostic test cases which depend on the observed symptoms and which permit the location of the detected faults. The algorithm guarantees the correct diagnosis of any single or double fault (output and/or transfer) in at most one of the transitions of a deterministic system which is represented by a set of communicating FSMs. A simple example is used to demonstrate the functioning of the different steps of the proposed diagnostic algorithm.<<ETX>>

Test generation for the distributed test architecture

ISO (International Standardization Organization) developed the ISO distributed test architecture for testing layered protocols. Furthermore, a general distributed test architecture where the IUT (implementation under test) contains several distributed ports is used for testing distributed systems, based on the Open Distributing Processing (ODP) Basic Reference Model (BRM). In this architecture, the testers cannot communicate or synchronize with one another unless they communicate through the IUT; and no global clock is available in the system. This architecture could model a test architecture of a communication network with n accessing nodes, where the testers reside in these nodes. When n=2, this general distributed test architecture reduces to the ISO distributed test architecture. The authors develop a test selection method with respect to this general distributed test architecture.

Diagnostic tests for communicating nondeterministic finite state machines

Systematic test sequence generation for conformance testing of communication protocol implementations, has been an active research area during the last decade. Methods were developed to produce optimized test sequences for detecting faults in such systems. However the application of these methods gives only limited information about the location of detected faults. In this paper we propose a complementary step, which localizes the fault, once detected. It consists of a generalized diagnostic algorithm for the case where distributed system specifications (implementations) are given in the form of communicating nondeterministic finite state machines. Such algorithm localizes the faulty transition once the fault has been detected. The algorithm guarantees the correct diagnosis of any single (output and/or transfer) fault. A simple example is used to demonstrate the functioning of the proposed algorithm. The complexity of each step in the algorithm and hence, the overall complexity are calculated.