Enhancing Valid Test Input Generation with Distribution Awareness for Deep Neural Networks

Comprehensive testing is important in improving the reliability of Deep Learning (DL)-based systems. Various Test Input Generators (TIGs) have been proposed to generate misbehavior-inducing test inputs. However, the lack of validity checking in TIGs often results in the generation of invalid inputs (i.e., out of the learned distribution), leading to unreliable testing. To save the effort of manually checking the validity and improve test efficiency, it is important to assess the effectiveness and reliability of automated validators. In this study, we comprehensively assess four automated Input Validators (IVs). Our findings show that the accuracy of IVs ranges from 49% to 77%. Distance-based IVs generally outperform reconstruction-based and density-based IVs for both classification and regression tasks. Based on the findings, we enhance existing testing frameworks by incorporating distribution awareness through joint optimization. The results demonstrate our framework leads to a 2% to 10% increase in the number of valid inputs, which establishes our method as an effective technique for valid test input generation.