Mutation testing in practice using Ruby

Block-based programming has been overwhelmingly successful in revitalizing introductory computing education and in facilitating end-user development. However, poor code quality makes block-based programs hard to understand, modify, and reuse, thus hurting the educational and productivity effectiveness of blocks. There is great potential benefit in empowering programmers in this domain to systematically improve the code quality of their projects. Refactoring--improving code quality while preserving its semantics--has been widely adopted in traditional software development. In this work, we introduce refactoring to Scratch. We define four new Scratch refactorings: Extract Custom Block, Extract Parent Sprite, Extract Constant, and Reduce Variable Scope. To automate the application of these refactorings, we enhance the Scratch programming environment with powerful program analysis and transformation routines. To evaluate the utility of these refactorings, we apply them to remove the code smells detected in a representative dataset of 448 Scratch projects. We also conduct a between-subjects user study with 24 participants to assess how our refactoring tools impact programmers. Our results show that refactoring improves the subjects' code quality metrics, while our refactoring tools help motivate programmers to improve code quality.

Mutation testing is the fault-based software testing approach that is widely applicable for assessing the effectiveness of a test suite. The test suite effectiveness is measured through artificial seeding of faults into the programs under test. Mutation testing tools (MTTs) are significant enablers of the conversion of mutation testing from the research perspective into the real life and mostly applicable testing process. Without using the automatic MTT, mutation testing can’t be really connected in this present reality and is unrealistic to be acknowledged by the industry. Authors analyze six open-source JAVA-based MTT (Jester, JavaMut, MuJava, Jumble, Judy, and Javalanche). The results are based on the performance of various JAVA programs and two real-life applications. Benchmark comparison among the MTT is presented in terms of mutants, mutation operator, mutation score, and quality output. On the basis of comparative analysis, the performance of each tool is explained with the protocol for finding the appropriate tool among the six MTTs. The results show that the MuJava performs best compared to the others.KeywordsMutation testingFault-based testingAdequacy criterionMutation testing tools

A probabilistic framework for mutation testing in deep neural networks

This chapter discusses the integration of ethical deliberations within agile software development processes. It emphasizes the importance of considering ethical implications during the development of software, not just AI. The chapter proposes modes of reflection and deliberation that include disclosive, weighing, and applicative modes of contemplation. It argues that these three kinds of thinking are guided by different normative values. The chapter suggests that agile development is an excellent starting point for implementing ethical deliberations, as it allows for continuous reflection and learning. It also proposes that development teams can perform this task themselves up to a point with proper guidance. This section further discusses the potential of agile processes to naturally accommodate ethical deliberation. However, it also acknowledges the challenges associated with implementing agile processes, especially in the context of machine learning models.

This chapter builds the foundation of software testing techniques by classifying the various testing approaches and testing coverage criteria. It gradually advances in the concepts and process of Mutation Testing and its application areas. Mutation testing has been applied at both the source code level and specification level of the software under test. Mutation testing, when applied to the source code, is named as Program Mutation. Similarly, when applied to the specifications, it is named as Specification Mutation. The relevant Mutation Testing tools available for different programming languages for both program and Specification Mutations are hereby listed. Owing to the high cost incurred in applying Mutation Testing to industrial needs, the on-going endeavors of the researchers in the area are elaborated here. Applying nature-inspired algorithms along with Mutation Testing for data generation/selection/minimization is an upcoming area of research. Search based Mutation Testing (SBMT) applies evolutionary techniques like Genetic Algorithms or other metaheuristic approaches for automating the tasks associated with mutation testing, which otherwise requires a lot of human effort, thus, making it a practical approach. This chapter concludes by giving the seminal recent advancements in the area.

Traditionally, mutation testing is used as test set generation and/or test evaluation criteria once it is considered a good fault model. This paper uses mutation testing for evaluating an automated static analyzer. Since static analyzers, in general, report a substantial number of false positive warnings, the intention of this study is to define a prioritization approach of static warnings based on their correspondence with mutations. On the other hand, knowing that Mutation Test has a high application cost, another possibility is to try to identify mutations of some specific mutation operators, which an automatic static analyzer is not adequate to detect. Therefore, this information can be used to prioritize the order of incrementally applying mutation operators considering, firstly, those with no correspondence with static warnings. In both cases, contributing to the establishment of incremental strategies on using automatic static analysis or mutation testing or even a combination of them. We used mutation operators as a fault model to evaluate the direct correspondence between mutations and static warnings. The main advantage of using mutation operators is that they generate a large number of programs containing faults of different types, which can be used to decide the ones most probable to be detected by static analyzers. We provide evidences on the correspondence between mutations and some types of static warnings. The results obtained for a set of 19 open-source programs indicate that: 1) static warnings may be prioritized based on their correspondence level with mutations; 2) specific set of mutation operators and their mutations may be prioritized based on their correspondence level with warnings. It is possible to provide an incremental testing strategy aiming at reducing the cost of both static analysis and mutation testing using the correspondence information between these activities/artifacts.

Mutation testing is a technique in which faults (mutants) are injected into a program or application to assess its test suite effectiveness. It works by inserting mutants and running the application’s test suite to identify if the mutants are detected (killed) or not (survived) by the tests. Although computationally expensive, it has proven to be an effective method to assess application test suites. Several mutation testing frameworks and tools have been built for the various programing languages, however, very few tools have been built for the JavaScript language, more specifically, there is a lack of mutation testing tools for the Node.js runtime and npm based applications. The npm Registry is a public collection of modules of open-source code for Node.js, front-end web applications, mobile applications, robots, routers, and countless other needs of the JavaScript community. The over 700,000 packages hosted in npm are downloaded more than 5 billion times per week. More and more software is published in npm every day, representing a huge opportunity to share code and solutions, but also to share bugs and faulty software. In this paper, we briefly describe prior work for mutation operators in JavaScript and Node.js, and propose Mutode, an open source tool which leverages the npm package ecosystem to perform mutation testing for JavaScript and Node.js applications. We empirically evaluated Mutode effectiveness by running it on 12 of the top 20 npm modules that have automated test suites.

Agile development processes such as Scrum have been successfully applied in the software industry for many years. Based on experience, industrial practitioners indicate three predominant benefits of agile development processes compared to traditional software development processes. First of all, development results better fit customers’ and other stakeholders’ needs. That is because they are intensively involved in the development process by receiving, applying and assessing functional software increments in a defined cadence throughout the development process. Secondly, agile development processes better cope with unexpected changes in the development process due to the built-in process flexibility. Lastly, development speed has significantly increased in most of the agile software development projects, resulting in a shorter time-to-market. Especially in the context of radical innovations for technical systems, manufacturing companies are striving for approaches to optimize their development processes in a similar direction. Traditional plan-oriented development approaches such as VDI 2221 or Cooper’s Stage-Gate Process turn out to be insufficiently customer oriented, too inflexible and project duration is usually too long to reach an adequate time-to-market. For that reason, a large community in academia and industrial practice is developing and implementing approaches to adapt agile software development practices for the development of technical systems. However, a current study in industrial practice reveals that out of 23 objectives, that are expected when introducing agile development processes to technical systems, the three objectives mentioned above, show the largest negative deviations from expected benefit to realized benefit. Therefore, the overall goal of this research is to address these gaps by developing an explicit methodological approach for an agile development of technical systems. It turns out, that mainly the role of prototyping and the way product specifications are handled during the development process change significantly in the course of introducing agility to development of technical systems. Agile practitioners strive to not necessarily define product specifications comprehensively upfront, as it is postulated in plan-oriented development processes. In contrast, product specifications, which are of major importance to the overall development project, are specified and validated with customers and other stakeholders in early prototypes. Therefore, prototypes are realized in a defined cadence throughout the development process to gradually specify and validate the product. However, the way product specifications are prioritized and selected in the development of technical systems has to differ substantially from the general way Scrum or other existing agile development processes propose. That is because technical systems are characterized by multiple technical interrelations, resulting in informational dependencies for the development process. For that reason, a prioritization along criteria such as customer value, development effort and risk seems too narrow in the context of technical systems. In fact, the prioritization of product specifications has to consider both, the value being generated by their realization as well as the informational dependencies towards other specifications. Furthermore, when designing a prototype, time constraints need to be particularly considered due to lead times in parts delivery and prototype production. Therefore, this paper introduces a methodology to prioritize and select technical design parameters in agile development processes. The methodology can be applied in the cyclical sprint planning that aims at defining the scope of the next prototype to be developed. As outlined above, the major paradigms of value generation, informational dependencies as well as lead-time and effort are crucial when adapting agile for technical systems and are consequently implemented in the methodology. These paradigms are operationalized to explicitly address the mentioned major objectives of agile development processes, which are currently showing are large gap between expected benefit and realized benefit in industrial practice. The methodology is applied to the real development process of an RGB laser light source for digital cinema projectors, which is summarized as a case study in the paper. Insights from this application are equally discussed as the resulting next steps in further developing and aligning the methodology to the needs of industrial practice.

Software Testing is one of the most significant phases within the software development life cycle since software bugs can be costly and traumatic. However, the traditional software testing process is not enough on its own as some undiscovered faults might still exist due to the test cases’ inability to detect all underlying faults. Amidst the various proposed techniques of test suites’ efficiency detection comes mutation testing, one of the most effective approaches as declared by many researchers. Nevertheless, there is not enough research on how well the mutation testing tools adhere to the theory of mutation or how well their mutation operators are performing the tasks they were developed for. This research paper presents an investigative study on two different mutation testing tools for Java programming language, namely PIT and µJava. The study aims to point out the weaknesses and strengths of each tool involved through performing mutation testing on four different open-source Java programs to identify the best mutation tool among them. The study aims to further identify and compare the mutation operators of each tool by calculating the mutation score. That is, the operators’ performance is evaluated with the mutation score, with the presumption that the more prominent the number of killed mutants is, the higher the mutation score, thus the more effective the mutation operator and the affiliated tool.Â

Semantic mutation testing

Testing Deep Learning (DL) systems is a complex task as they do not behave like traditional systems would, notably because of their stochastic nature. Nonetheless, being able to adapt existing testing techniques such as Mutation Testing (MT) to DL settings would greatly improve their potential verifiability. While some efforts have been made to extend MT to the Supervised Learning paradigm, little work has gone into extending it to Reinforcement Learning (RL) which is also an important component of the DL ecosystem but behaves very differently from SL. This paper builds on the existing approach of MT in order to propose a framework, RLMutation, for MT applied to RL. Notably, we use existing taxonomies of faults to build a set of mutation operators relevant to RL and use a simple heuristic to generate test cases for RL. This allows us to compare different mutation killing definitions based on existing approaches, as well as to analyze the behavior of the obtained mutation operators and their potential combinations called Higher Order Mutation(s) (HOM). We show that the design choice of the mutation killing definition can affect whether or not a mutation is killed as well as the generated test cases. Moreover, we found that even with a relatively small number of test cases and operators we manage to generate HOM with interesting properties which can enhance testing capability in RL systems.

Aspect-Oriented Programming (AOP) is a contemporary software development technique that strongly relies on the Separation of Concerns principle. It aims to tackle software modularisation problems by introducing the aspect as a new implementation unit to encapsulate behaviour required to realise the so-called crosscutting concerns. Despite the benefits that may be achieved with AOP, its implementation mechanisms represent new potential sources of faults that should be handled during the testing phase. In this context, mutation testing is a widely investigated fault-based test selection criterion that can help to demonstrate the absence of prespecified faults in the software. It is believed to be an adequate tool to deal with testing-related specificities of contemporary programming techniques such as AOP. However, to date, the few initiatives for customising the mutation testing for aspect-oriented (AO) programs show either limited coverage with respect to the types of simulated faults, or a need for both adequate tool support and proper evaluation. This thesis tackles these limitations by defining a comprehensive mutation-based testing approach for AO programs written in the AspectJ language. It starts with a fault-proneness investigation in order to define a fault taxonomy for AO software. Such taxonomy encompasses a range of fault types and underlay the definition of a set of mutation operators for AO programs. Automated tool support is also provided. A series of quantitative studies show that the proposed fault taxonomy is able to categorise faults identified from several available AO systems. Moreover, the studies show that the mutation operators are able to simulate faults that may not be revealed by pre-existing, non-mutation-based test suites. Furthermore, the effort required to augment the test suites to provide adequate coverage of mutants does not tend to overwhelm the testers. This provides evidence of the feasibility of the proposed approach and represents a step towards the practical fault-based testing of AO programs.

Achieving comprehensive code quality and ensuring software reliability are critical goals in modern software engineering. This paper delves into advanced strategies that encompass both technical and organizational practices, aiming to enhance code quality and boost software reliability. Key strategies include the implementation of rigorous code review processes, adoption of automated testing frameworks, and the utilization of static and dynamic code analysis tools. Firstly, rigorous code review processes are fundamental for maintaining high standards of code quality. By fostering a collaborative environment where peer reviews are routine, teams can catch potential issues early, ensure adherence to coding standards, and promote knowledge sharing. This practice not only improves code quality but also enhances team cohesion and expertise. Secondly, automated testing frameworks are indispensable in achieving comprehensive test coverage and reducing the incidence of bugs. Unit tests, integration tests, and end-to-end tests, when automated, provide continuous feedback and ensure that code changes do not introduce new defects. This continuous testing approach is crucial for maintaining software reliability, especially in agile and DevOps environments where rapid iterations are common. Furthermore, the integration of static and dynamic code analysis tools into the development pipeline offers additional layers of quality assurance. Static analysis tools inspect the codebase for potential vulnerabilities, code smells, and compliance with coding standards without executing the program. Dynamic analysis tools, on the other hand, evaluate the software during runtime to detect memory leaks, concurrency issues, and performance bottlenecks. Together, these tools provide a comprehensive assessment of the code’s health and reliability. Moreover, fostering a culture of continuous improvement and learning within the development team is essential. Regular training sessions, workshops, and knowledge-sharing activities help in keeping the team updated with the latest advancements in software engineering practices and tools. Encouraging a mindset of quality-first and reliability among developers ensures long-term benefits and sustainability. In conclusion, achieving comprehensive code quality and ensuring software reliability require a multifaceted approach that integrates rigorous code reviews, automated testing frameworks, and both static and dynamic analysis tools. Coupled with a strong culture of continuous learning and improvement, these strategies collectively contribute to the development of robust, reliable, and high-quality software systems. Keywords: Software Reliability, Code Quality, Advanced, Strategies, Comprehensive.

Mutation testing is a well known technique for estimating and improving the quality of test suites. Given a test suite T for a system S, mutation testing systematically creates mutants of S and executes T to measure how many mutants T detects. If T does not detect some (non-equivalent) mutants, T can be improved by adding test cases that detect those mutants. Mutants are created by applying mutation operators. Mutation operators are important because they define the characteristics of the system that are tested as well as the characteristics that are improved in the test suite. While mutation operators are well defined for a number of programming paradigms such as sequential or multi-threaded, to the best of our knowledge, mutation operators have not been defined for the actor programming model. In this paper, we define and classify mutation operators that can be used for mutation testing of actor programs.

A testing criterion is a predicate to be satisfied and generally addresses two important questions related to: 1) the selection of test cases capable of revealing as many faults as possible; and 2) the evaluation of a test set to consider the test ended. Studies show that fault based criteria, such as mutation testing, are very efficacious, but very expensive in terms of the number of test cases. Mutation testing uses mutation operators to generate alternatives for the program P under test. The goal is to derive test cases to producing different behaviours in P and its alternatives. This approach usually does not allow the test of interaction between faults since the alternative differs from P by a simple modification. This work explores the use of Genetic Programming (GP) to derive alternatives for testing P and describes two GP-based test procedures for selection and evaluation of test data. Experimental results show the GP approach applicability and allow comparison with mutation testing.