Yong Rae Kwon

MuJava: an automated class mutation system

Several module and class testing techniques have been applied to object‐oriented (OO) programs, but researchers have only recently begun developing test criteria that evaluate the use of key OO features such as inheritance, polymorphism, and encapsulation. Mutation testing is a powerful testing technique for generating software tests and evaluating the quality of software. However, the cost of mutation testing has traditionally been so high that it cannot be applied without full automated tool support. This paper presents a method to reduce the execution cost of mutation testing for OO programs by using two key technologies, mutant schemata generation (MSG) and bytecode translation. This method adapts the existing MSG method for mutants that change the program behaviour and uses bytecode translation for mutants that change the program structure. A key advantage is in performance: only two compilations are required and both the compilation and execution time for each is greatly reduced. A mutation tool based on the MSG/bytecode translation method has been built and used to measure the speedup over the separate compilation approach. Experimental results show that the MSG/bytecode translation method is about five times faster than separate compilation. Copyright

Inter-class mutation operators for Java

The effectiveness of mutation testing depends heavily on the types of faults that the mutation operators are designed to represent. Therefore, the quality of the mutation operators is key to mutation testing. Mutation testing has traditionally been applied to procedural-based languages, and mutation operators have been developed to support most of their language features. Object-oriented programming languages contain new language features, most notably inheritance, polymorphism, and dynamic binding. Not surprisingly; these language features allow new kinds of faults, some of which are not modeled by traditional mutation operators. Although mutation operators for OO languages have previously been suggested, our work in OO faults indicate that the previous operators are insufficient to test these OO language features, particularly at the class testing level. This paper introduces a new set of class mutation operators for the OO language Java. These operators are based on specific OO faults and can be used to detect faults involving inheritance, polymorphism, and dynamic binding, thus are useful for inter-class testing. An initial Java mutation tool has recently been completed, and a more powerful version is currently under construction.

A cohesion measure for object-oriented classes

In object‐oriented systems, cohesion refers to the degree of the relatedness of the members in a class and strong cohesion has been recognized as a highly desirable property of classes. We note that the existing cohesion measures do not take into account some characteristics of classes, and thus often fail to properly reflect the cohesiveness of classes. To cope with such a problem, we propose a new cohesion measure where the characteristics of classes are incorporated. Our cohesion measure takes into account the members that actually have impact on the cohesiveness of a class, and is defined in terms of the degree of the connectivity among those members.

Integration and analysis of use cases using modular Petri nets in requirements engineering

It is well known that requirements engineering plays a critical role in software quality. The use case approach is a requirements elicitation technique commonly used in industrial applications. Software requirements are stated as a collection of use cases, each of which is written in the users perspective and describes a specific flow of events in the system. The use case approach offers several practical advantages in that use case requirements are relatively easy to describe, understand, and trace. Unfortunately, there are a couple of major drawbacks. Since use cases are often stated in natural languages, they lack formal syntax and semantics. Furthermore, it is difficult to analyze their global system behavior for completeness and consistency, partly because use cases describe only partial behaviors and because interactions among them are rarely represented explicitly. We propose the Constraints-based Modular Petri Nets (CMPNs) approach as an effective way to formalize the informal aspects of use cases. CMPNs, an extension of Place/Transition nets, allow the formal and incremental specification of requirements. The major contributions of the paper, in addition to the formal definitions of CMPNs, are the development of: 1) a systematic procedure to convert use cases stated in natural language to a CMPN model; and 2) a set of guidelines to find inconsistency and incompleteness in CMPNs. We demonstrate an application of our approach using use cases developed for telecommunications services.

The class-level mutants of MuJava

This paper presents results from empirical studies of object-oriented, class level mutation operators, using the automated analysis and testing tool MuJava. Class mutation operators modify OO programming language features such as inheritance, polymorphism, dynamic binding and encapsulation. This paper presents data from 866 classes in six open-source programs. Several new class-level mutation operators are defined in this paper and an analysis of the number of mutants generated is provided. Techniques for eliminating some equivalent mutants are described and data from an automated tool are provided. One important result is that class-level mutation operators yield far more equivalent mutants than traditional, statement-level, operators. Another is that there are far fewer class-level mutants than statement-level mutants. Together, these data suggest that mutation for inter-class testing can be practically affordable.

Testing of object-oriented programs based on finite state machines

In object-oriented testing literature, a class is considered to be a basic unit of testing. A major characteristic of classes is the interaction between data members and member functions. This interaction is represented as definitions and uses of data members in member functions and can be properly modeled with finite state machines (FSM). We discuss how FSMs can be effectively used for class testing. We demonstrate how to specify the behavior of classes using FSMs and present a test case generation technique based on FSMs. In our technique, FSMs are transformed into a flow of the graph from which we can explicitly identify data flows of the FSM. Then we generate test cases using conventional data flow testing techniques upon the flow graph.

A cohesion measure for classes in object-oriented systems

Classes are the fundamental concepts in the object-oriented paradigm. They are the basic units of object-oriented programs, and serve as the units of encapsulation, which promotes the modifiability and the reusability of them. In order to take full advantage of the desirable features provided by classes, such as data abstraction and encapsulation, classes should be designed to have good quality. Because object-oriented systems are developed by heavily reusing the existing classes, the classes of poor quality can be a serious obstacle to the development of systems. We define a new cohesion measure for assessing the quality of classes. Our approach is based on the observations on the salient natures of classes which have not been considered in the previous approaches. A Most Cohesive Component (MCC) is introduced as the most cohesive form of a class. We believe that the cohesion of a class depends on the connectivity of itself and its constituent components. We propose the connectivity factor to indicate the degree of the connectivity among the members of a class, and the structure factor to take into account the cohesiveness of its constituent components. Consequently, the cohesion of a class is defined as the product of the connectivity factor and the structure factor. This cohesion measure indicates how closely a class approaches MCC; the closely a class approaches MCC, the greater cohesion the class has.

Improving cohesion metrics for classes by considering dependent instance variables

The existing cohesion metrics for classes do not consider the characteristics of dependent instance variables that are commonly used in a class and, thus, do not properly reflect the cohesiveness of the class. This paper presents an approach for improving the cohesion metrics by considering the characteristics of the dependent instance variables in an object-oriented program.

An empirical evaluation of six methods to detect faults in software

Although numerous empirical studies have been conducted to measure the fault detection capability of software analysis methods, few studies have been conducted using programs of similar size and characteristics. Therefore, it is difficult to derive meaningful conclusions on the relative detection ability and cost‐effectiveness of various fault detection methods. In order to compare fault detection capability objectively, experiments must be conducted using the same set of programs to evaluate all methods and must involve participants who possess comparable levels of technical expertise. One such experiment was ‘Conflict1’, which compared voting, a testing method, self‐checks, code reading by stepwise refinement and data‐flow analysis methods on eight versions of a battle simulation program. Since an inspection method was not included in the comparison, the authors conducted a follow‐up experiment ‘Conflict2’, in which five of the eight versions from Conflict1 were subjected to Fagan inspection. Conflict2 examined not only the number and types of faults detected by each method, but also the cost‐effectiveness of each method, by comparing the average amount of effort expended in detecting faults. The primary findings of the Conflict2 experiment are the following. First, voting detected the largest number of faults, followed by the testing method, Fagan inspection, self‐checks, code reading and data‐flow analysis. Second, the voting, testing and inspection methods were largely complementary to each other in the types of faults detected. Third, inspection was far more cost‐effective than the testing method studied. Copyright

Evaluation of mutation testing for object-oriented programs

The effectiveness of mutation testing depends heavily on the types of faults that the mutation operators are designed to represent. Thus, the quality of the mutation operators is key to mutation testing. Although, mutation operators for object-oriented languages have previously been presented, little research has been done to show the usefulness of the class mutation operators. To assess the usefulness of class mutation operators, we conducted two empirical studies. In the first study, we examine the number and kinds of mutants that are generated for object-oriented programs. In the second study, we investigate the way in which class mutation operators model faults that are not detected by traditional mutation testing. We conducted our studies using a well-known object-oriented system, BCEL.