A User Feedback Centric Approach for Detecting and Mitigating God Class Code Smell Using Frequent Usage Patterns

Code smells are the fragments in the source code that indicates deeper problems in the underlying software design. These code smells can hinder software evolution and maintenance. Out of different code smell types, the God Class (GC) code smell is one of the many important code smells that directly affects the software evolution and maintenance. The GC is commonly defined as a much larger class in systems that either know too much or do too much as compared to other classes in the system. God Classes are generally accidentally created overtime during software evolution because of the incremental addition of functionalities to it. Generally, a GC indicates a bad design choice and it must be detected and mitigated in order to enhance the quality of the underlying software. However, sometimes the presence of a GC is also considered a good design choice, especially in compiler design, interpreter design and parser implementation. This makes the developer’s feedback important for the correct classification of a class as a GC or a normal class. Therefore, this paper proposes a new approach that detects and proposes refactoring opportunities for GC code smell. The proposed approach makes use of different code metrics in combination along with utilizing user feedback as an important aspect while correctly identifying the GC code smell. The proposed approach that considers combined use of code metrics, is based on two newly proposed code metrics in this paper. The first newly proposed metric is a new approach of measuring the connectivity of a given class with other classes in the system (also termed as coupling). The second newly proposed code metric is proposed to measure the extent to which a given classes make use of foreign member variables. Finally, the proposed approach is also empirically evaluated on two standard open-source commonly used software systems. The obtained result indicates that the proposed approach is capable of correctly identifying the GC code smell

An exploratory study of fault-proneness in evolving aspect-oriented programs

This paper presents the results of an exploratory study on the fault- proneness of aspect-oriented programs. We analysed the faults collected from three evolving aspect-oriented systems, all from different application domains. The analysis develops from two different angles. Firstly, we measured the impact of the obliviousness property on the fault-proneness of the evaluated systems. The results show that 40% of reported faults were due to the lack of awareness among base code and aspects. The second analysis regarded the fault-proneness of the main aspect-oriented programming (AOP) mechanisms, namely pointcuts, advices and intertype declarations. The results indicate that these mechanisms present similar fault-proneness when we consider both the overall system and concern- specific implementations. Our findings are reinforced by means of statistical tests. In general, this result contradicts the common intuition stating that the use of pointcut languages is the main source of faults in AOP

Scalable Model-based Robustness Testing: Novel Methodologies and Industrial Application

Embedded systems, as for example communication and control systems, are being increasingly used in our daily lives and hence require thorough and systematic testing before their actual use. Many of these systems interact with their environment and, therefore, their functionality is largely dependent on this environment whose behavior can be unpredictable. Robustness testing aims at testing the behavior of a system in the presence of faulty situations in its operating environment (e.g., sensors and actuators). In such situations, the system should gracefully degrade its performance instead of abruptly stopping execution. To systematically perform robustness testing, one option is to resort to Model-Based Robustness Testing (MBRT), which is a systematic, rigorous, and automated way of conducting robustness testing. However, to successfully apply MBRT in industrial contexts, new technologies need to be developed to scale to the complexity of real industrial systems. This thesis presents a solution for MBRT on industrial systems, including scalable robustness modeling and executable test case generation. One important contribution of this thesis is a scalable RobUstness Modeling Methodology (RUMM), which is achieved using Aspect-Oriented Modeling (AOM). It is a complete, automated, and practical methodology that covers all features of state machines and aspect concepts necessary for MBRT. Such methodology, relying on a standard (Unified Modeling Language or UML) and using the target notation as the basis to model the aspects themselves, is expected to make the practical adoption of robustness modeling easier in industrial contexts. The applicability of the methodology is demonstrated using an industrial case study. Results showed that the approach significantly reduced modeling effort (98% on average), improved separation of concerns, and eased model evolution. The approach is further empirically evaluated using two controlled experiments involving human subjects and results showed that the proposed methodology significantly improves the readability of models as compared to modeling using standard UML notations. Another important contribution of this thesis is an efficient approach for solving constraints (written in Objects Constraint Language (OCL)) on the operating environment of a system, which is mandatory for emulating faulty situation in the environment for the purpose of MBRT. A set of novel heuristics is devised for various OCL constructs, which are required for the application of search algorithms. The heuristics have been empirically evaluated on an industrial case study for robustness testing and the results showed to be very promising and significantly better than the existing works in the literature on OCL constraint solvers. A final contribution of the thesis is robustness test case generation from the models developed using RUMM. Test case generation also includes scripts generation for environment emulation, which is mandatory for automated robustness testing again using an industrial case study. In preliminary experiments, the execution of test cases found one critical, robustness fault in a deployed industrial system