Most automated program repair methods rely on test cases to determine the correctness of the generated patches. However, due to the incompleteness of available test suites, some patches that pass all the test cases may still be incorrect. This issue is known as the patch overfitting problem. Overfitting problem is a longstanding problem in automated program repair. Due to overfitting patches, the patches obtained by automated program repair tools require further validation to determine their correctness. Researchers have proposed many methods to automatically assess the correctness of patches, but no systematic review provides a detailed introduction to this problem, the existing solutions, and the challenges. To address this deficiency, we systematically review the existing approaches to patch correctness assessment. We first offer a few examples of overfitting patches to acquire a more detailed understanding of this problem. We then propose a comprehensive categorization of publicly available techniques and datasets, examine the commonly used evaluation metrics, and perform an in-depth analysis of the effectiveness of the existing models in addressing the challenge of overfitting. Based on our analysis, we provided the difficulties encountered by current methodologies, alongside the possible avenues for future research exploration.

In recent years, pre-trained language models have seen significant success in natural language processing and have been increasingly applied to code-related tasks. Code intelligence tasks have shown promising performance with the support of code pre-trained language models. Pre-processing code simplification methods have been introduced to prune code tokens from the model’s input while maintaining task effectiveness. These methods improve the efficiency of code intelligence tasks while reducing computational costs. Post-prediction code simplification methods provide explanations for code intelligence task outcomes, enhancing the reliability and interpretability of model predictions. However, comprehensive evaluations of these methods across diverse code pre-trained model architectures and code intelligence tasks are lacking. To assess the effectiveness of code simplification methods, we conduct an empirical study integrating these code simplification methods with various pre-trained code models across multiple code intelligence tasks. Our empirical findings suggest that developing task-specific code simplification methods would be beneficial. Then, we recommend leveraging post-prediction methods to summarize prior knowledge, which can pre-process code simplification strategies. Moreover, establishing more evaluation mechanisms for code simplification is crucial. Finally, we propose incorporating code simplification methods into the pre-training phase of code pre-trained models to enhance their program comprehension and code representation capabilities.