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3D point cloud applications have become increasingly prevalent in diverse domains, showcasing their efficacy in various software systems. However, testing such applications presents unique challenges due to the high-dimensional nature of 3D point cloud data and the vast number of possible test cases. Test input prioritization has emerged as a promising approach to enhance testing efficiency by prioritizing potentially misclassified test cases during the early stages of the testing process. Consequently, this enables the early labeling of critical inputs, leading to a reduction in the overall labeling cost. However, applying existing prioritization methods to 3D point cloud data is constrained by several factors: (1) inadequate consideration of crucial spatial information, and (2) susceptibility to noises inherent in 3D point cloud data. In this article, we propose PCPrior, the first test prioritization approach specifically designed for 3D point cloud test cases. The fundamental concept behind PCPrior is that test inputs closer to the decision boundary of the model are more likely to be predicted incorrectly. To capture the spatial relationship between a point cloud test and the decision boundary, we propose transforming each test (a point cloud) into a low-dimensional feature vector, toward indirectly revealing the underlying proximity between a test and the decision boundary. To achieve this, we carefully design a group of feature generation strategies, and for each test input, we generate four distinct types of features, namely spatial features, mutation features, prediction features, and uncertainty features. Through a concatenation of the four feature types, PCPrior assembles a final feature vector for each test. Subsequently, a ranking model is employed to estimate the probability of misclassification for each test based on its feature vector. Finally, PCPrior ranks all tests based on their misclassification probabilities. We conducted an extensive study based on 165 subjects to evaluate the performance of PCPrior, encompassing both natural and noisy datasets. The results demonstrate that PCPrior outperforms all of the compared test prioritization approaches, with an average improvement of 10.99% to 66.94% on natural datasets and 16.62% to 53% on noisy datasets. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive survey on test optimization in deep neural network (DNN) testing. Here, test optimization refers to testing with low data labeling effort. We analyzed 90 papers, including 43 from the software engineering (SE) community, 32 from the machine learning (ML) community, and 15 from other communities. Our study: (i) unifies the problems as well as terminologies associated with low-labeling cost testing, (ii) compares the distinct focal points of SE and ML communities, and (iii) reveals the pitfalls in existing literature. Furthermore, we highlight the research opportunities in this domain. [ABSTRACT FROM AUTHOR]

Code search is a common yet important activity of software developers. An efficient code search model can largely facilitate the development process and improve the programming quality. Given the superb performance of learning the contextual representations, deep learning models, especially pre-trained language models, have been widely explored for the code search task. However, studies mainly focus on proposing new architectures for ever-better performance on designed test sets but ignore the performance on unseen test data where only natural language queries are available. The same problem in other domains, e.g., CV and NLP, is usually solved by test input selection that uses a subset of the unseen set to reduce the labeling effort. However, approaches from other domains are not directly applicable and still require labeling effort. In this article, we propose the kNN-based performance testing (KAPE) to efficiently solve the problem without manually matching code snippets to test queries. The main idea is to use semantically similar training data to perform the evaluation. Extensive experiments on six programming language datasets, three state-of-the-art pre-trained models, and seven baseline methods demonstrate that KAPE can effectively assess the model performance (e.g., CodeBERT achieves MRR 0.5795 on JavaScript) with a slight difference (e.g., 0.0261). [ABSTRACT FROM AUTHOR]

Applying deep learning (DL) to science is a new trend in recent years, which leads DL engineering to become an important problem. Although training data preparation, model architecture design, and model training are the normal processes to build DL models, all of them are complex and costly. Therefore, reusing the open-sourced pre-trained model is a practical way to bypass this hurdle for developers. Given a specific task, developers can collect massive pre-trained deep neural networks from public sources for reusing. However, testing the performance (e.g., accuracy and robustness) of multiple deep neural networks (DNNs) and recommending which model should be used is challenging regarding the scarcity of labeled data and the demand for domain expertise. In this article, we propose a labeling-free (LaF) model selection approach to overcome the limitations of labeling efforts for automated model reusing. The main idea is to statistically learn a Bayesian model to infer the models' specialty only based on predicted labels. We evaluate LaF using nine benchmark datasets, including image, text, and source code, and 165 DNNs, considering both the accuracy and robustness of models. The experimental results demonstrate that LaF outperforms the baseline methods by up to 0.74 and 0.53 on Spearman's correlation and Kendall's τ, respectively. [ABSTRACT FROM AUTHOR]

Graph Neural Networks (GNNs) have achieved promising performance in a variety of practical applications. Similar to traditional DNNs, GNNs could exhibit incorrect behavior that may lead to severe consequences, and thus testing is necessary and crucial. However, labeling all the test inputs for GNNs can be costly and time-consuming, especially when dealing with large and complex graphs, which seriously affects the efficiency of GNN testing. Existing studies have focused on test prioritization for DNNs, which aims to identify and prioritize fault-revealing tests (i.e., test inputs that are more likely to be misclassified) to detect system bugs earlier in a limited time. Although some DNN prioritization approaches have been demonstrated effective, there is a significant problem when applying them to GNNs: They do not take into account the connections (edges) between GNN test inputs (nodes), which play a significant role in GNN inference. In general, DNN test inputs are independent of each other, while GNN test inputs are usually represented as a graph with complex relationships between each test. In this article, we propose GraphPrior (GNN-oriented Test Prioritization), a set of approaches to prioritize test inputs specifically for GNNs via mutation analysis. Inspired by mutation testing in traditional software engineering, in which test suites are evaluated based on the mutants they kill, GraphPrior generates mutated models for GNNs and regards test inputs that kill many mutated models as more likely to be misclassified. Then, GraphPrior leverages the mutation results in two ways, killing-based and feature-based methods. When scoring a test input, the killing-based method considers each mutated model equally important, while feature-based methods learn different importance for each mutated model through ranking models. Finally, GraphPrior ranks all the test inputs based on their scores. We conducted an extensive study based on 604 subjects to evaluate GraphPrior on both natural and adversarial test inputs. The results demonstrate that KMGP, the killing-based GraphPrior approach, outperforms the compared approaches in a majority of cases, with an average improvement of 4.76% ~49.60% in terms of APFD. Furthermore, the feature-based GraphPrior approach, RFGP, performs the best among all the GraphPrior approaches. On adversarial test inputs, RFGP outperforms the compared approaches across different adversarial attacks, with the average improvement of 2.95% ~46.69%. [ABSTRACT FROM AUTHOR]

Context: When software evolves, opportunities for introducing faults appear. Therefore, it is important to test the evolved program behaviors during each evolution cycle. However, while software evolves, its complexity is also evolving, introducing challenges to the testing process. To deal with this issue, testing techniques should be adapted to target the effect of the program changes instead of the entire program functionality. To this end, commit-aware mutation testing, a powerful testing technique, has been proposed. Unfortunately, commit-aware mutation testing is challenging due to the complex program semantics involved. Hence, it is pertinent to understand the characteristics, predictability, and potential of the technique. Objective: We conduct an exploratory study to investigate the properties of commit-relevant mutants, i.e., the test elements of commit-aware mutation testing, by proposing a general definition and an experimental approach to identify them. We thus aim at investigating the prevalence, location, and comparative advantages of commit-aware mutation testing over time (i.e., the program evolution). We also investigate the predictive power of several commit-related features in identifying and selecting commit-relevant mutants to understand the essential properties for its best-effort application case. Method: Our commit-relevant definition relies on the notion of observational slicing, approximated by higher-order mutation. Specifically, our approach utilizes the impact of mutants, effects of one mutant on another in capturing and analyzing the implicit interactions between the changed and unchanged code parts. The study analyses millions of mutants (over 10 million), 288 commits, five (5) different open-source software projects involving over 68,213 CPU days of computation and sets a ground truth where we perform our analysis. Results: Our analysis shows that commit-relevant mutants are located mainly outside of program commit change (81%), suggesting a limitation in previous work. We also note that effective selection of commitrelevant mutants has the potential of reducing the number of mutants by up to 93%. In addition, we demonstrate that commit relevant mutation testing is significantly more effective and efficient than state-of-the-art baselines, i.e., random mutant selection and analysis of only mutants within the program change. In our analysis of the predictive power of mutants and commit-related features (e.g., number of mutants within a change, mutant type, and commit size) in predicting commit-relevant mutants, we found that most proxy features do not reliably predict commit-relevant mutants. Conclusion: This empirical study highlights the properties of commit-relevant mutants and demonstrates the importance of identifying and selecting commit-relevant mutants when testing evolving software systems. [ABSTRACT FROM AUTHOR]

This article, published in the journal "Software Testing: Verification & Reliability," features two papers on fault tolerance and metamorphic relation prediction. The first paper discusses a system architecture called perception simplex (PS) that aims to achieve fault tolerance against perception faults in autonomous vehicles for collision avoidance. The authors demonstrate that PS provides deterministic fault tolerance against obstacle existence detection faults. The second paper explores the effectiveness of code representation learning techniques for predicting metamorphic relations (PMR) and shows that code representation learning can positively contribute to the prediction of MRs. The authors hope that these papers will inspire further research in related areas. [Extracted from the article]

This article discusses two different contributions in the field of software testing. The first contribution focuses on detecting unsafe code in the Rust programming language and proposes a tool called SafeNet that identifies and mitigates unnecessary unsafe code. The second contribution addresses the need for thorough testing of autonomous driving systems (ADSs) and introduces a novel testing approach called MetaSem, which uses semantic information of driving scenes to identify inconsistent behaviors. Both contributions aim to improve the reliability and correctness of complex software systems. [Extracted from the article]

A fundamental part of the self‐healing grid is reducing disturbances and automatically responding to problems. Toward this goal, smart grid operators would be of great use to ensure stability after a potential overload for a planning horizon, as the electrical values are unknown. To evaluate the robustness of the topology reconfiguration after a disturbance, like an overload, reliability analysis through simulation can be employed. However, the simulation approach we propose in this paper, except for the excessive time it consumes, cannot assure the quality of its solutions. To achieve a more robust configuration, we, additionally, propose a single‐stage stochastic program to optimize the grid topology configuration after a potential overload to ensure stability for the next day. We suggest a simheuristic approach based on a Variable Neighborhood Search metaheuristic to solve the above stochastic optimization problem. We evaluate the two approaches for this real‐world problem, together with Creos Luxembourg S.A., the leading grid operator in Luxembourg. We show that our method can quickly suggest countermeasures to operators facing potential overloading incidents, ensuring the smart grid's stability for the next day. [ABSTRACT FROM AUTHOR]

This article discusses two papers that examine different aspects of software reliability using fault injection techniques. The first paper investigates the impact of transient hardware faults on deep learning neural network inference, particularly in safety-critical applications like autonomous vehicles and healthcare systems. The authors enhance fault injection techniques to reveal the significant influence of hardware faults on these applications. The second paper addresses the challenges of fault localization in software debugging and presents a novel approach, Delta4Ms, that mitigates mutant bias and improves fault localization accuracy. These papers provide valuable insights into ensuring software reliability and resilience in different contexts. [Extracted from the article]

Recent successes in training word embeddings for Natural Language Processing (NLP) tasks have encouraged a wave of research on representation learning for source code, which builds on similar NLP methods. The overall objective is then to produce code embeddings that capture the maximum of program semantics. State-of-the-art approaches invariably rely on a syntactic representation (i.e., raw lexical tokens, abstract syntax trees, or intermediate representation tokens) to generate embeddings, which are criticized in the literature as non-robust or non-generalizable. In this work, we investigate a novel embedding approach based on the intuition that source code has visual patterns of semantics. We further use these patterns to address the outstanding challenge of identifying semantic code clones. We propose the WySiWiM (''What You See Is What It Means") approach where visual representations of source code are fed into powerful pre-trained image classification neural networks from the field of computer vision to benefit from the practical advantages of transfer learning. We evaluate the proposed embedding approach on the task of vulnerable code prediction in source code and on two variations of the task of semantic code clone identification: code clone detection (a binary classification problem), and code classification (a multi-classification problem). We show with experiments on the BigCloneBench (Java), Open Judge (C) that although simple, ourWySiWiMapproach performs as effectively as state-of-the-art approaches such as ASTNN or TBCNN. We also showed with data from NVD and SARD that WySiWiM representation can be used to learn a vulnerable code detector with reasonable performance (accuracy ~90%).We further explore the influence of different steps in our approach, such as the choice of visual representations or the classification algorithm, to eventually discuss the promises and limitations of this research direction. [ABSTRACT FROM AUTHOR]

This article from the journal "Software Testing: Verification & Reliability" features two papers that focus on different aspects of software testing and vulnerability detection. The first paper introduces directed greybox fuzzing (DGF) as an effective approach for uncovering bugs in software. It analyzes various fuzzers related to DGF and discusses its benefits, limitations, and potential areas for future research. The second paper proposes a tensor-based gated graph neural network called TensorGNN for automatic vulnerability detection in source code. This model outperforms existing works in terms of accuracy and training time, offering a novel perspective on vulnerability detection. Overall, these papers contribute to the improvement of software quality and provide avenues for further research in these areas. [Extracted from the article]

This article, published in the journal "Software Testing: Verification & Reliability," features two papers on test case prioritization and mutation testing. The first paper introduces the SatTCP framework, which uses information retrieval techniques and a pretrained Siamese network to prioritize test cases for continuous integration testing. The evaluation results show that SatTCP outperforms other methods and achieves the lowest test costs. The second paper investigates the use of the Clang front-end for implementing mutation optimization strategies in the C language family. The authors develop a proof-of-concept tool and evaluate it on several libraries, finding that certain steps in the mutation process are more time-consuming than others. The authors hope that these papers will inspire further research in related areas. [Extracted from the article]

We introduce SEMu, a Dynamic Symbolic Execution technique that generates test inputs capable of killing stubborn mutants (killable mutants that remain undetected after a reasonable amount of testing). SEMu aims at mutant propagation (triggering erroneous states to the program output) by incrementally searching for divergent program behaviors between the original and the mutant versions. We model the mutant killing problem as a symbolic execution search within a specific area in the programs’ symbolic tree. In this framework, the search area is defined and controlled by parameters that allow scalable and cost-effective mutant killing. We integrate SEMu in KLEE and experimented with Coreutils (a benchmark frequently used in symbolic execution studies). Our results show that our modeling plays an important role in mutant killing. Perhaps more importantly, our results also show that, within a two-hour time limit, SEMu kills 37% of the stubborn mutants, where KLEE kills none and where the mutant infection strategy (strategy suggested by previous research) kills 17%. [ABSTRACT FROM AUTHOR]

Testing of deep learning models is challenging due to the excessive number and complexity of the computations involved. As a result, test data selection is performed manually and in an ad hoc way. This raises the question of how we can automatically select candidate data to test deep learning models. Recent research has focused on defining metrics to measure the thoroughness of a test suite and to rely on such metrics to guide the generation of new tests. However, the problem of selecting/prioritising test inputs (e.g., to be labelled manually by humans) remains open. In this article, we perform an in-depth empirical comparison of a set of test selection metrics based on the notion of model uncertainty (model confidence on specific inputs). Intuitively, the more uncertain we are about a candidate sample, the more likely it is that this sample triggers a misclassification. Similarly, we hypothesise that the samples for which we are the most uncertain are the most informative and should be used in priority to improve the model by retraining. We evaluate these metrics on five models and three widely used image classification problems involving real and artificial (adversarial) data produced by five generation algorithms. We show that uncertainty-based metrics have a strong ability to identify misclassified inputs, being three times stronger than surprise adequacy and outperforming coverage-related metrics. We also show that these metrics lead to faster improvement in classification accuracy during retraining: up to two times faster than random selection and other state-of-the-art metrics on all models we considered. [ABSTRACT FROM AUTHOR]

This article, published in the journal "Software Testing: Verification & Reliability," features three papers on different aspects of software testing. The first paper discusses the transformation of model-based tests into code and highlights the limitations and implications for future research in this area. The second paper presents evaluation strategies for a hyper-heuristic framework for multi-objective test case prioritization, identifying the best performing strategy. The third paper explores the use of deep reinforcement learning and metamorphic testing for automatically testing virtual reality applications, showing promising results. The authors hope that these papers will inspire further research in these fields. [Extracted from the article]

When the proof fails, Proof2Test uses the counterexample generated by the prover to produce a failed test, which provides the programmer with immediately exploitable information to correct the programme. The key assumption behind Proof2Test is that programme proofs (static) and programme tests (dynamic) are complementary rather than exclusive: proofs bring the absolute certainties that tests lack but are abstract and hard to get right; tests cannot guarantee correctness but, when they fail, bring the concreteness of counterexamples, immediately understandable to the programmer. The Groucho approach conducts in vivo testing of Java applications transparently, not necessarily requiring any source code modification nor even source code availability. [Extracted from the article]

The authors empirically investigate the effectiveness and scalability of the data flow subsumptions by applying data flow testing on programs. In this issue as a special issue of ICST 2021, we are pleased to present two papers, one for supervision of deep neural network and the other for data flow testing. [Extracted from the article]