EMPIRICAL CHARACTERIZATION OF SOFTWARE QUALITY

The research topic focuses on the characterization of software quality considering the main software elements such as people, process and product. Many attributes (size, language, testing techniques etc.) probably could have an effect on the quality of software. In this thesis we aim to understand the impact of attributes of three P’s (people, product, process) on the quality of software by empirical means. Software quality can be interpreted in many ways, such as customer satisfaction, stability and defects etc. In this thesis we adopt ‘defect density’ as a quality measure. Therefore the research focus on the empirical evidences of the impact of attributes of the three P’s on the software defect density. For this reason empirical research methods (systematic literature reviews, case studies, and interviews) are utilized to collect empirical evidence. Each of this research method helps to extract the empirical evidences of the object under study and for data analysis statistical methods are used. Considering the product attributes, we have studied the size, language, development mode, age, complexity, module structure, module dependency, and module quality and their impact on project quality. Considering the process attributes, we have studied the process maturity and structure, and their impact on the project quality. Considering the people attributes, we have studied the experience and capability, and their impact on the project quality. Moreover, in the process category, we have studied the impact of one testing approach called ‘exploratory testing’ and its impact on the quality of software. Exploratory testing is a widely used software-testing practice and means simultaneous learning, test design, and test execution. We have analyzed the exploratory testing weaknesses, and proposed a hybrid testing approach in an attempt to improve the quality. Concerning the product attributes, we found that there exist a significant difference of quality between open and close source projects, java and C projects, and large and small projects. Very small and defect free modules have impact on the software quality. Different complexity metrics have different impact on the software quality considering the size. Product complexity as defined in Table 53 has partial impact on the software quality. However software age and module dependencies are not factor to characterize the software quality. Concerning the people attributes, we found that platform experience, application experience and language and tool experience have significant impact on the software quality. Regarding the capability we found that programmer capability has partial impact on the software quality where as analyst capability has no impact on the software quality. Concerning process attributes we found that there is no difference of quality between the project developed under CMMI and those that are not developed under CMMI. Regarding the CMMI levels there is difference of software quality particularly between CMMI level 1 and CMMI level 3. Comparing different process types we found that hybrid projects are of better quality than waterfall projects. Process maturity defined by (SEI-CMM) has partial impact on the software quality. Concerning exploratory testing, we found that exploratory testing weaknesses induce the testing technical debt therefore a process is defined in conjunction with the scripted testing in an attempt to reduce the associated technical debt of exploratory testing. The findings are useful for both researchers and practitioners to evaluate their project

Empirical studies on exploratory software testing

Exploratory software testing (ET) is a practically relevant approach to software testing that lacks scientific knowledge. In ET, the tester's work is not based on predesigned and documented test cases. Instead, testing is guided by a higher-level plan or mission, and the testing work involves parallel test design, test execution, and learning. One of the distinct characteristics of ET is that the tester designs the tests during ET and uses information gained to design new and better tests continuously. The ET approach relies on testers' skills and experience. The main claimed benefits of ET are the tester's ability to apply personal knowledge and creativity during testing as well as effectiveness, efficiency, and agility in terms of adapting to changes and working with imperfect documentation. In this thesis, the ET approach has been studied using empirical research methods. Two case studies, one controlled experiment, and two field studies were performed to address three research goals: defining ET and understanding its applicability based on the literature; empirically investigating the benefits and shortcomings of ET; and providing empirically based results on how the ET approach is applied in practice. This research identifies different approaches to ET in industry and describes concrete testing practices. The role of the tester's personal knowledge is identified in the literature, and this research provides a detailed analysis of the application of personal knowledge in failure detection using ET. The main conclusions of this work are that ET can be as effective as test case-based approaches and even more efficient in certain contexts. The testers are capable of utilizing their personal knowledge in failure detection, and the role of personal knowledge is important in the ET approach. In addition, software testing in product organizations seems to involve multiple diverse organizational groups, and ET was found to be an applicable approach to engage domain experts in testing. The main implications of this thesis are introducing the exploratory testing approach to the research community and motivating its relevance by providing empirical studies in industry. In addition, the results of the effectiveness and efficiency of ET as well as the qualitative data on exploratory testing practices and the detailed analysis of knowledge in exploratory testing work are valuable for the research community. The main practical implications include presenting the benefits and applicability of the ET approach along with the potential shortcomings and providing empirical evidence regarding the benefits of ET