Pei Hsia

Formal approach to scenario analysis

Scenarios offer promise as a way to tame requirements analysis, but progress has been impeded by the lack of a systematic way to analyze, generate, and validate them. The authors propose such a method and apply it to a simple PBX system. Their method has a formal mathematical base, generates precise scenarios, accommodates change, and keeps users involved in the process.<<ETX>>

An object-oriented web test model for testing Web applications

In recent years, Web applications have grown rapidly. As Web applications become complex, there is a growing concern about their quality and reliability. In this paper we present a methodology that uses an object-oriented Web Test Model (WTM) to support Web application testing. The test model captures both structural and behavioral test artifacts of Web applications and represents the artifacts form the object, behavior and structure perspectives. Based on the test model, both structural and behavioral test cases can be derived automatically to ensure the quality of Web applications. Moreover the model also can be used as a road map to identify change ripple effects and to find cost-effective testing strategies for reducing test efforts required in the regression testing.

Status report: requirements engineering

It is argued that, in general, requirements engineering produces one large document, written in a natural language, that few people bother to read. Projects that do read and follow the document often build systems that do not satisfy needs. The reasons for the current state of the practice are listed. Research areas that have significant payoff potential, including improving natural-language specifications, rapid prototyping and requirements animation, requirements clustering, requirements-based testing, computer-aided requirements engineering, requirements reuse, research into methods, knowledge engineering, formal methods, and a unified framework, are outlined.<<ETX>>

On regression testing of object-oriented programs

Regression testing is an important activity in software maintenance. Although a number of studies have addressed the problems and solutions in regression testing of traditional programs, no studies have focused on the issues and solutions in regression testing of object-oriented programs. In this article, we discuss various types of code changes of classes in an object-oriented program and present a method for identifying these changes and the affected classes. An algorithm for generating a desirable order to test the affected classes is also described. The basic model we use is an object relation graph, which depicts the inheritance, aggregation, and association relations that exist in the object-oriented program to be maintained. The test order generation algorithm can be applied to acyclic as well as cyclic object relation graphs. The results of this work have been implemented and applied to testing of many example applications, including the InterViews library.

Developing an object-oriented software testing and maintenance environment

The object-oriented (OO) paradigm is rapidly gaining acceptance in the software industry. However, the powerful features of this new paradigm also introduce a new set of OO software testing and maintenance problems. The pioneering work in identifying these new problems includes [7, 10-12, 14, 16, 18]. The problems can be summarized as: 1) the understanding problem; 2) the complex interdependency problem; 3) the object state behavior testing problem; and 4) the tool support problem. Detailed discussions of these problems will be provided later. Our industrial experience confirms these discoveries.

On object state testing

The importance of object state testing is illustrated through a simple example. We show that certain errors in the implementation of object state behavior cannot be readily detected by conventional structural testing, functional testing, and state testing. We describe an object state test model and outline a reverse engineering method for extracting object state behaviors from C++ source code. The object state test model is a hierarchical, concurrent, communicating state machine. It resembles the concepts of inheritance and aggregation in the object-oriented paradigm rather than the concept of state decomposition as in some existing models. The reverse engineering method is based on symbolic execution to extract the states and effects of the member functions. The symbolic execution results are used to construct the state machines. The usefulness of the model and of the method is discussed in the context of object state testing in the detection of a state behavior error.<<ETX>>

Object-based data flow testing of web applications

Recently, the extraordinary growth in the World Wide Web has been sweeping through business and industry. Many companies have developed or integrated their mission-critical applications using Web technologies. As Web applications become complex, testing Web applications becomes crucial. This paper extends traditional data flow testing techniques to Web applications. Several data flow issues for analyzing HTML documents in Web applications are discussed. A test model that captures data flow test artifacts of Web applications is presented. In the test model, each component of a Web application is modeled as an object. The data flow information of the Web application is captured using flow graphs. From the test model, data flow test cases for the Web application then can be derived based on the intra-object, inter-object, and inter-client perspectives.

An object-oriented Web test model for testing Web applications

Recently the number of Web applications has increased immensely. Many businesses have been using Web applications for their mission-critical operations. As Web applications become complex, their quality and reliability become crucial. The paper describes an object oriented test model that captures both structural and behavioral test artifacts of Web applications. The model represents the entities of Web applications as objects and describes their structures, relationships, and dynamic behaviors. Based on the test model, test methods are presented to derive test cases automatically for ensuring the structures and behaviors of Web applications.

A test strategy for object-oriented programs

The complexity and interdependencies of an object oriented program makes testing of such programs difficult. We present a reverse engineering based model called Object Relation Diagram (ORD), which is generated from analyzing the C++ source code of an object oriented program. An ORD is a directed graph in which the vertices represent the object classes and the edges represent the relationships among the object classes. Based on the ORD, a test strategy, called test order, for unit testing and integration testing of object oriented programs is described. The test order algorithm uses topological sorting and clusters of strongly connected subgraphs of the ORD. It computes the optimal test order in the sense that the effort required to construct the test stubs to simulate the untested classes/member functions is minimum. We show the savings of the test strategy through statistics of the InterViews library.

A technique for the selective revalidation of OO software

The object-orientated paradigm provides the power for software development but at the same time introduces some brand new problems. One of these problems is that the relationships among classes are more complex and difficult to identify than those in the traditional paradigm. This problem becomes a major obstacle for regression testing of OO software, in which the relationships among classes as well as those between test cases and classes, must be determined a priori. In this paper we propose a new method to select only a fraction of the test cases from the entire test suite to revalidate an OO software system. This method is based on the concepts of class firewall and of marking all the classes ‘touched’ by a test case. From the class firewall, we can identify all of the affected classes after a new version of software is released. Together with the markings, we can also identify all the test cases in the test suite that need to be retested after the software change. A step-by-step process is proposed to identify the relationships between classes and test cases, compute the class firewall, and select only the appropriate test cases for retesting.