OCL-Based Test Case Optimisation with Modified APFD Metric

Abstract

Testing is one of the most time-consuming and unpredictable processes within the software development life cycle. As a result, many Test Case Optimisation (TCO) techniques have been proposed to make this process more scalable. Object Constraint Language (OCL) was initially introduced as a constraint language to provide additional details to UML models. However, as OCL continues to evolve, an increasing number of systems are being expressed by this language. Despite this growth, a noticeable research gap exists for the testing of systems whose specifications are expressed in OCL. In our previous work, we verified the effectiveness and efficiency of performing the Test Case Prioritisation (TCP) process for these systems. In this study, we extend our previous work by integrating the Test Case Minimisation (TCM) process to determine whether TCM can also benefit the testing process under the context of OCL. The evaluation of TCO approaches often relies on well-established metrics such as the Average Percentage of Fault Detection (APFD). However, the suitability of APFD for Model-Based Testing (MBT) is not ideal. This paper addresses this limitation by proposing a modification to the APFD metric to enhance its viability for MBT scenarios. We conducted four case studies to evaluate the feasibility of integrating the TCM and TCP processes in our proposed approach. In these studies, we applied the multi-objective optimisation algorithm NSGA-II and the genetic algorithm independently to the TCM and TCP processes. The objective was to assess the effectiveness and efficiency of combining TCM and TCP in enhancing the testing phase. Through experimental analysis, the results highlight the benefits of integrating TCM and TCP in the context of OCL-based testing, providing valuable insights for practitioners and researchers aiming to optimise their testing efforts. Specifically, the main contributions of this work include: 1). We introduce the integration of the TCM process into the TCO process for systems expressed by OCL. This integration benefits the testing process further by reducing redundant test cases while ensuring sufficient coverage. 2). We comprehensively analyse the limitations associated with the commonly used metric, APFD, and then a modified version of the APFD metric has been proposed to overcome these weaknesses. 3). We systematically evaluate the effectiveness and efficiency of OCL-based TCO processes on four real-world case studies with different complexities.