Paving the Way for Self-driving Cars - Software Testing for Safety-critical Systems Based on Machine Learning : A Systematic Mapping Study and a Survey

Abstract: Context: With the development of artificial intelligence, autonomous vehicles are becoming more and more feasible and the safety of Automated Driving (AD) system should be assured. This creates a need to analyze the feasibility of verification and validation approaches when testing safety-critical system that contains machine learning (ML) elements. There are many studies published in the context of verification and validation (V&V) research area related to safety-critical components. However, there are still blind spots of research to identify which test methods can be used to test components with deep learning elements for AD system. Therefore, research should focus on researching the relation of test methods and safety-critical components, also need to find more feasible V&V testing methods for AD system with deep learning structure. Objectives: The main objectives of this thesis is to understand the challenges and solution proposals related to V&V of safety-critical systems that rely on machine learning and provide recommendations for future V&V of AD based on deep learning, both for research and practice. Methods: We performed a Systematic Literature Review (SLR) through a snowballing method, based on the guidelines from Wohlin [1], to identify research on V&V methods development for machine learning. A web-based survey was used to complement the result of literature review and evaluate the V&V challenge and methods for machine learning system. We identified 64 peer-reviewed papers and analysed the methods and challenges of V&V for testing machine learning components. We conducted an industrial survey that was answered by 63 subjects. We analyzed the survey results with the help of descriptive statistics and Chi-squared tests. Result: Through the SLR we identified two peaks for research on V&V of machine learning. Early research focused on the aerospace field and in recent years the research has been more active in other fields like automotive and robotics. 21 challenges during V&V safety-critical systems have been described and 32 solution proposals are addressing the challenges have been identified. To find the relationship between challenges and methods, a classification has been done that seven different type of challenges and five different type of solution proposals have been identified. The classification and mapping of challenges and solution methods are included in the survey questionnaire. From the survey, it was observed that some solution proposals which have attracted much research are not considered as particularly promising by practitioners. On the other hand, some new solution methods like simulated test cases are extremely promising to support V&V for safety-critical systems. Six suggestions are provided to both researchers and practitioners. Conclusion: To conclude the thesis, our study presented a classification of challenges and solution methods for V&V of safety-critical ML-based systems. We also provide a mapping for helping practitioners understand the different kinds of challenges the respective solution methods address. Based on our findings, we provide suggestions to both researchers and practitioners. Thus, through the analysis, we have given the most concern on types of challenges and solution proposals for AD systems that use deep learning, which provides certain help to design processes for V&V of safety-critical ML-based systems in the future.