Extended Finite State Machine Model Research Articles

A Research for Executable Path Automatic Generation Method Based on EFSM

Extended finite state machine (EFSM) is currently one of the most widely used model in the field of software testing. EFSM model is an enhanced model based on finite state machine (FSM). Automated test data generation is still a challenging problem due to the complexity of EFSM which extends the input and output parameters, context variables as well as the predicate condition. These reasons lead to conflict of the context variable with the enable conditions in the transition path. In order to avoid infeasible path generation, this paper proposes a method based on modified breadth first search to generate feasible transition path (MBFS-FTP). To solve the problem of state explosion in path generation, this paper converts state diagram to transition diagram on EFSM model. In order to make the EFSM static model can be driven execution, this paper uses UML model and generate executable model, so that implements EFSM execute dynamically. When using breadth-first search algorithm (MBFS) on every target transition to generate an executable transition path, the conflict detection algorithm is utilized to the transition path for conflict decision, avoiding the occurrence of an infeasible transition path. Considering target transition has multiple feasible transition paths, this paper combines suggested penalized value of definition-predicate-use (def-p-use) pair and length of feasible transition path, and then develops the measurement method of feasible transition path, and obtained a set of feasible transition path containing all of transitions. Through the experiment on two actual EFSM model, verifying the effectiveness of MBFS-FTP for feasible transition automatic generation, the experimental results show that MBFS-FTP can reduce the feasible transition path length, and make transition paths are more easily to be triggered at the times of generating test cases lately, furthermore, it can improve the efficiency of generate feasible transition path and save a lot of time.

An EFSM-Based Test Data Generation Approach in Model-Based Testing

Testing is an integral part of software development. Current fast-paced system developments have rendered traditional testing techniques obsolete. Therefore, automated testing techniques are needed to adapt to such system developments speed. Model-based testing (MBT) is a technique that uses system models to generate and execute test cases automatically. It was identified that the test data generation (TDG) in many existing model-based test case generation (MB-TCG) approaches were still manual. An automatic and effective TDG can further reduce testing cost while detecting more faults. This study proposes an automated TDG approach in MB-TCG using the extended finite state machine model (EFSM). The proposed approach integrates MBT with combinatorial testing. The information available in an EFSM model and the boundary value analysis strategy are used to automate the domain input classifications which were done manually by the existing approach. The results showed that the proposed approach was able to detect 6.62 percent more faults than the conventional MB-TCG but at the same time generated 43 more tests. The proposed approach effectively detects faults, but a further treatment to the generated tests such as test case prioritization should be done to increase the effectiveness and efficiency of testing.

Generating feasible protocol test sequences from EFSM models using Monte Carlo tree search

Feasible test sequences generation is a key step in protocol conformance testing based on the Extended Finite State Machine (EFSM) model. To guarantee the feasibility of generated test sequences, transition executability analysis (TEA) technique is widely applied in automatic test derivation. However, the TEA method often suffers from the famous state explosion problem, which has become a major obstacle to its efficient application.

Diversity-Oriented Test Suite Generation for EFSM Model

In this article, test diversity has been suggested to be a valid way to improve test suite effectiveness. Extended finite state machine (EFSM) is a widely used formal model, but little attention is paid on the test suite generation with more diversity. EFSM test suite generation involves test paths generation and test data generation. Considering the discrepancy between test paths has a more crucial impact on the diversity of test suite, compared with the difference between test data, this article, therefore, mainly concerns the test paths generation with more diversity for EFSM models. Hence, the factors that influence the discrepancy between test paths are investigated. Then based on these factors, an integrated distance metric is designed to evaluate the dissimilarity between test paths, and a diversity measurement for EFSM test suite is presented. Furthermore, a diversity-oriented test suite generation (DOTSG) method is proposed where a dissimilarity-based fitness function and diversity-oriented update strategy are adopted in traditional coverage-oriented EFSM test suite generation (COTSG) by genetic algorithm. The experimental results show that, compared to COTSG, our DOTSG can not only generate more diverse test suite to satisfy a certain coverage criteria, improving the fault detection capability of the test suite, but also decrease the evolution time cost and the size of test suite generated.

A Test Generation Method for EFSM-based Protocols Using the Transitions Feasibility Estimation

Although extensive studies have been done on the protocol conformance testing based on an extended finite state machine (EFSM) model, the automatic generation of feasible test sequences is still a challenging task. A generated test sequence may be infeasible, due to the conflicts among the transition conditions and context variables of EFSMs. This paper proposed a test sequence generation approach for EFSM-based protocols conformance test by using the transition feasibility estimation. Firstly, our method generates candidate transition paths from a directed graph G which is derived from the EFSM model under testing ignoring all the predicates; Then, we designed a fitness function to guide the test generation with a trade-off among path feasibility, coverage criterion and path length. Finally, an adaptive exploration algorithm is developed to generate executable test sequences through expanding CPs. An experiment was designed to validate the effectiveness of the proposed method with two classic EFSM models. The experimental results show that our approach is more effective by comparing it to the TEA method based on breadth-first search (BFS).

Toward automatically quantifying the impact of a change in systems

Software maintenance is becoming more challenging with the increased complexity of the software and the frequently applied changes. Performing impact analysis before the actual implementation of a change is a crucial task during system maintenance. While many tools and techniques are available to measure the impact of a change at the code level, only a few research work is done to measure the impact of a change at an earlier stage in the development process. Measuring the impact of a change at the model level speeds up the maintenance process allowing early discovery of critical components of the system before applying the actual change at the code level. In this paper, we present model-based impact analysis approach for state-based systems such as telecommunication or embedded systems. The proposed approach uses model dependencies to automatically measure the expected impact for a requested change instead of relying on the expertise of system maintainers, and it generates two impact sets representing the lower bound and the upper bound of the impact. Although it can be extended to other behavioral models, the presented approach mainly addresses extended finite-state machine (EFSM) models. An empirical study is conducted on six EFSM models to investigate the usefulness of the proposed approach. The results show that on average the size of the impact after a single modification (a change in a one EFSM transition) ranges between 14 and 38 % of the total size of the model. For a modification involving multiple transitions, the average size of the impact ranges between 30 and 64 % of the total size of the model. Additionally, we investigated the relationships (correlation) between the structure of the EFSM model, and the size of the impact sets. Upon preliminary analysis of the correlation, the concepts of model density and data density were defined, and it was found that they could be the major factors influencing the sizes of impact sets for models. As a result, these factors can be used to determine the types of models for which the proposed approach is the most appropriate.

Генерация функциональных тестов для HDL-описаний на основе проверки моделей

Automated test generation is a promising direction in hardware verification research area. Functional test generation methods based on models are widespread at the moment. In this paper, a functional test generation method based on model checking is proposed and compared to existing solutions. Automated model extraction from the hardware design’s source code is used. Supported HDLs include VHDL and Verilog. Several kinds of models are used at different steps of the test generation method: guarded action decision diagram (GADD), high-level decision diagram (HLDD) and extended finite-state machine (EFSM). The high-level decision diagram model (which is extracted from the GADD model) is used as a functional model. The extended finite-state machine model is used as a coverage model. The aim of test generation is to cover all the transitions of the extended finite state machine model. Such criterion leads to the high HDL source code coverage. Specifications based on transition and state constraints of the EFSM are extracted for this purpose. Later, the functional model and the specifications are automatically translated into the input format of the nuXmv model checking tool. nuXmv performs model checking and generates counterexamples. These counterexamples are translated to functional tests that can be simulated by the HDL simulator. The proposed method has been implemented as a part of the HDL Retrascope framework. Experiments show that the method can generate shorter tests than the FATE and RETGA methods providing the same or better source code coverage.

A framework for compositional nonblocking verification of extended finite-state machines

This paper presents a framework for compositional nonblocking verification of discrete event systems modelled as extended finite-state machines (EFSM). Previous results are improved to consider general conflict-equivalence based abstractions of EFSMs communicating both via shared variables and events. Performance issues resulting from the conversion of EFSM systems to finite-state machine systems are avoided by operating directly on EFSMs, deferring the unfolding of variables into state machines as long as possible. Several additional methods to abstract EFSMs and remove events are also presented. The proposed algorithm has been implemented in the discrete event systems tool Supremica, and the paper presents experimental results for several large EFSM models that can be verified faster than by previously used methods.

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Model-based test generation is widely spread in functional verification of hardware designs. The extended finite state machine (EFSM) is known to be a powerful formalism for modelling digital hardware. As opposed to conventional finite state machines, EFSM models separate datapath and control, which makes it possible to represent systems in a more compact way and, in a sense, reduces the risk of state explosion during verification. In this paper, a new EFSM-based test generation approach is proposed and compared with the existing solutions. It combines random walk on a state graph and directed search of feasible paths. The first phase allows covering “easy-to-fire” transitions. The second one is aimed at “hard-to-fire” cases; the algorithm tries to build a path that enables a given transition; it is carried out by analyzing control and data dependencies and applying symbolic execution techniques. Experiments show that the suggested approach provides better transition coverage with shorter test sequences comparing to the known methods and achieves a high level of code coverage.

一种基于扩展有限状态机的自动化测试用例生成方法

Extended finite state machine (EFSM) is among the most popular models for model-based testing. However, automated test case generation on EFSM models is still a challenging task since an EFSM model may contains infeasible paths. This paper proposed a novel approach (ATGEM) to generate test case and construct oracle information from EFSM automatically. To address the infeasible problem, a metric based on data flow analysis is presented to predict the infeasible probability so as to bypass the infeasible paths as far as possible and improve the test case generation efficiency. Afterwards, an executable EFSM model is developed to obtain runtime feedback information as a fitness function in order to generate test data and construct oracle information automatically. This approach, which can generate various types data and has a wide range of applications, combines static analysis and dynamic analysis aims to find a preferable feasible path subset to generate test cases and meet adequacy coverage criteria. The experimental results on several EFSM models show that test case generation method and path feasibility metric have good effectiveness. Utilizing path feasibility metric can speed up the process of test case generation greatly, and ATGEM is more efficient than existing method.

A Visual EFSM Modeling System for Protocol Testing

An Extended Finite State Machine (EFSM) is one of the most popular models used in protocol testing field. A specific graphical EFSM model consists of two parts: state elements and transition elements. This paper presents a method for building a visual EFSM modeling system (VEMS), which is used to construct visual protocol EFSM models for protocol testing. VEMS consists of two main modules. One is the modeling module and the other is the model information analysis module. The function of our system can satisfy the requirements to build a visual EFSM model in protocol testing. Specially, users can modify the properties of states and transitions, change the size of states and transitions, build connection between states and transitions, etc. VEMS provides a good modeling support for protocol testing. Its advantages include friendly user interface, simple modeling operation, model persistence and recovery.

An EFSM Approach to Software Design Based on the Supervisory Control Theory

The research of software design, based on the supervisory control theory, is an important content in software cybernetics. The existing software model used in the software design with the supervisory control theory is Polynomial Dynamic System (PDS), which is transformed from SIGNAL files. This obstructs its widespread application. Extended Finite State Machine (EFSM) model is widely applied in software engineering field and it may alleviate the state explosion problem of Finite State Machine (FSM) to some extent. In this paper, the EFSM model is suggested to study software design problem. This paper proposed two kinds of software design problems based on EFSM model. For the first problem, a necessary and sufficient condition for software existence is obtained. For the second problem, a necessary and sufficient condition for software existence and an optimal algorithm to such software design are presented.

Fault masking by multiple timing faults in timed EFSM models

Detection of multiple timing faults is a challenging task because these faults, although may be detectable individually, can mask each other's faulty behavior, making a faulty implementation under test (IUT) indistinguishable from a non-faulty one during testing. This phenomenon, called fault masking, is formally defined in this paper. It is proven that graph augmentation algorithms proposed for timed Extended Finite State Machines (EFSMs) with multiple timers can detect pairwise occurrences of classes of timing faults in an IUT and, hence, detects fault masking.

Fault Modeling and Detection Capabilities for EFSM Models

Inherent timing variables and constraints in communication protocols require new extended finite-state machine (EFSM) models to formally represent their behavior, particularly for test generation purposes. However, infeasible paths due to the conflicts among the timing condition and action variables in the timed EFSM models with the activation and expiration of concurrent timers complicate the test generation process. In a test measurement laboratory, such timers, if not properly taken into account by formal methods at the test generation step, can generate false results by failing correct implementations or, worse, passing faulty implementations. This paper analyzes the fault detection capability of the timed EFSM models introduced in our earlier work in the presence of multiple timing faults. It is proven that, for a class of timing faults, test sequences generated from our models can detect multiple occurrences of pairwise combinations of such faults. A simplified version of the session initiation protocol (SIP) registration process, which is widely used by voice over IP (VoIP) telephones, has been used as a working example throughout this paper.

A method enabling feasible conformance test sequence generation for EFSM models

A formal description of an implementation under test (IUT), such as its VHDL behavior description, is required to automatically generate feasible test sequences for the IUT. Although finite-state machines (FSMs) can be used to describe the control structures of communication protocols, the data portion can only be modeled by extended finite-state machines (EFSMs). However, infeasible paths due to the conflicts among the condition and action variables of EFSMs complicate the test generation process. We introduce a method enabling the automatic generation of realizable test sequences from a class of EFSMs. Algorithms to detect and eliminate conflicts caused by the interdependences among the variables of a class of EFSM models are presented. After all conflicts are eliminated from the EFSM graph, the existing FSM-based automated test generation methods can be used to generate feasible test sequences. Recently, these algorithms have been implemented as a software package called INDEEL. This methodology is applied to generate feasible tests for protocols such as ACA and MIL-STD 188-220. Current applications include IETF protocols and ASAP.

Automatic test case derivation for communication protocols in an extended FSM model

This paper considers the extended finite-state machine model (EFSM/Pres), which has several registers to retain integer values, in addition to the controller of the finite-state machine. A new method is proposed for automatically generating the test sequence for the conformance test, called the E-UIO sequence, from the formal specification of the communication protocol written by that model. In EFSM/Pres, the data type to be handled is restricted to the integer type. The condition for each transition is described by a logical expression composed of addition/subtraction and comparison of integers. For this class, the input/output sequence composed of the UIO sequence and its precedence sequence is considered. By inputting adequate values to the input variables of the sequence, if the input/output sequences are executable regardless of the register values at the start state of the precedence sequence, that input/output sequence is called an E-UIO sequence. The existence of the state to be recognized is verified by using the E-UIO sequence. If the given UIO sequence is executable, an E-UIO sequence containing the definite input values is always generated automatically. A method to generate automatically a test sequence that verifies the validity of the transition is also proposed. As an example, the proposed method is applied to the OSI session protocol. © 1999 Scripta Technica, Electron Comm Jpn Pt 1, 82(10): 50–60, 1999

Automatic generation of functional vectors using the extended finite state machine model

We present a method of automatic generation of functional vectors for sequential circuits. These vectors can be used for design verification, manufacturing testing, or power estimation. A high-level description of the circuit in VHDL or C is assumed available. Our method automatically transforms the high-level description of a circuit in VHDL or C into an extended finite state machine (EFSM) model that is used to generate functional vectors. The EFSM model is a generalization of the traditional state machine model. It is a compact representation of models with local data variables and preserves many nice properties of a traditional state machine model. The theoretical background of the EFSM model is addressed in this article. Our method guarantees that the generated vectors cover every statement in the high-level description at least once. Experimental results show that a set of comprehensive functional vectors for sequential circuits with more than a hundred flip-flops can be generated automatically in a few minutes of CPU time using our prototype system.

Estelle-based test generation tool

A test design tool for functional analysis and test derivation of protocols formally specified using an extended finitestate machine model is presented. The formal description language supported is Estelle. The tool's main components include a compiler, a normalizer, a multiple module transition tour generator and several interactive programs. The tool is based on a static analysis of Estelle called normalization, which is explained in detail with various examples. The normalized specification facilitates graphical displays of the control and data flow in the specification by the interactive tools. Next discussed is test generation, which is based on verifying the control and data flow. First the data flow graph must be decomposed into blocks where each block represents the data flow in a protocol function. From the control graph the tool generates transition tours, and then test sequences are derived from the transition tour to test each function. The performance of the tool on various applications is also included.

Method of analysing extended finite-state machine specifications

Formal specifications are the basis for automated verification and implementation in communication software. The paper gives a method of dynamic analysis for modular specifications which is based on symbolic execution and reachability analysis. Symbolic execution is a technique for static analysis and applied first to the specification. It is effective in detecting syntactic and semantic errors. A form of reachability analysis, called limited reachability, is used to dynamically analyse the intermodule communication. It has two applications: combining modules and detecting any errors in intermodule communication. The technique is first applied to the specifications in a nondeterministic finite-state machine model and then applied to an extended finite-state machine model for which two standard formal description languages exist.