Search-based Test Case Generation (TCG) for web applications suffers from unstable performance and suboptimal test suite problems due to diversity loss. However, previous diversity metrics mainly only focus on client-side models or server-side code, which are prone to low robustness and poor generalization in practical applications. We propose a diversity-driven TCG method DTester, which can maximize behavior exploration and minimize the test suite size while covering more server-side vulnerable paths. Three diversity metrics (i.e. phenotypic coupling, intent coupling and competitiveness) are proposed to measure the underlying relationship between test cases from user behavior, code logic and test execution history. Moreover, a 3-dimensional weight graph is designed to model association among metrics, which provides fine-grained guidance for the genetic algorithm to generate diverse test cases from the client-side behavior model. Our empirical evaluation on five web applications shows that DTester can efficiently and robustly generate better test suites than the state-of-the-art TCG method. The maximum improvement is [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in efficiency, test suite size, diversity and robustness.

Fault Localization (FL) is one of the most essential and time-consuming steps during software debugging. Mutation-based fault localization (MBFL) is one FL technique that has demonstrated promising fault localization accuracy in recent years. Current MBFL techniques mainly use First-Order Mutant (FOM) to localize faults, and only perform well in simple fault localization. When facing complex fault localization, MBFL with FOMs can only achieve low FL accuracy. Moreover, previous Higher-Order Mutant (HOM) generation techniques only use simple combinations of FOMs but do not consider the correlation between simple faults in the composition of complex faults. In this study, we consider the relationships between single faults and propose SFClu, a novel HOM generation method. Specifically, SFClu aims to generate HOMs to simulate complex faults consisting of multiple unrelated simple faults on multiple lines. To evaluate the performance of our proposed methods, we conduct empirical studies on 237 complex-fault programs from two datasets. The experimental results show that SFClu significantly outperforms traditional HOM generation methods (i.e., Last2First, DifferentOperators, and RandomMix). Furthermore, the experimental results also demonstrate that Higher-Order MBFL(HMBFL) with SFClu can outperform the state-of-the-art SBFL and MBFL techniques in terms of EXAM, TOP-N, and MAP metrics.

Mutation-based fault localization has shown promising accuracy in localizing faults due to its finer analysis granularity. However, the effectiveness is limited when dealing with diverse real-world systems and actual faults, which results from its inflexible suspiciousness calculation and oversimplification of information. In this work, we propose a novel Mutation-Based Fault Localization technique, GMBFL, which utilizes Graph representation to achieve multi-information cooperation to improve fault localization. GMBFL comprises two key components: a fine-grained graph-based representation to fully utilize the information of the program, and an effective suspiciousness measure using the graph neural network to learn useful features from the graph. We evaluate GMBFL on 243 real faulty programs from Defects4J. The experimental results show that GMBFL can surpass both the state-of-the-art learning-based fault localization technique and 70 commonly used SBFL and MBFL techniques. In particular, GMBFL localizes 125 faults within TOP-1 whereas the best baseline technique can at most localize 109 faults within TOP-1.

Automatically localizing faulty statements is a desired feature for effective learning programming. Most of the existing automated fault localization techniques are developed and evaluated on commercial or well-known open-source projects, which performed poorly on novice programs. In this paper, we propose a novel fault localization technique VsusFL (Variable-suspiciousness-based Fault Localization) for novice programs. VsusFL is inspired by simulating the manual program debugging process and takes advantage of variable value sequences. VsusFL can trace variable value changes, determine whether the intermediate state of the variables is correct, and report the potential faulty statements for novice programs. This paper presents the implementation of VsusFL and conducts empirical studies on 422 real faulty novice programs. Experimental results show that VsusFL performs much better than Grace, ANGELINA, VSBFL, Spectrum-Based Fault Localization (SBFL), and Variable-based Fault Localization (VFL) in terms of T O P -1, T O P -3, and T O P -5 metrics. Specifically, VsusFL can localize 90%, 35% and 9% more faulty statements than the best-performing baseline Grace. Moreover, We analyze the correlation between VsusFL and other techniques and find a weak correlation since they perform well on different programs, indicating the potential to further enhance fault localization performance through strategic integration of VsusFL with other methods.