The Foundation Cracks: A Comprehensive Study on Bugs and Testing Practices in LLM Libraries

Fuente: arXiv
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Hauptverfasser: Jiang, Weipeng, Zhang, Xiaoyu, Xie, Xiaofei, Yu, Jiongchi, Zhi, Yuhan, Ma, Shiqing, Shen, Chao
Format: Preprint
Veröffentlicht: 2025
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author Jiang, Weipeng
Zhang, Xiaoyu
Xie, Xiaofei
Yu, Jiongchi
Zhi, Yuhan
Ma, Shiqing
Shen, Chao
author_facet Jiang, Weipeng
Zhang, Xiaoyu
Xie, Xiaofei
Yu, Jiongchi
Zhi, Yuhan
Ma, Shiqing
Shen, Chao
contents Large Language Model (LLM) libraries have emerged as the foundational infrastructure powering today's AI revolution, serving as the backbone for LLM deployment, inference optimization, fine-tuning, and production serving across diverse applications. Despite their critical role in the LLM ecosystem, these libraries face frequent quality issues and bugs that threaten the reliability of AI systems built upon them. To address this knowledge gap, we present the first comprehensive empirical investigation into bug characteristics and testing practices in modern LLM libraries. We examine 313 bug-fixing commits extracted across two widely-adopted LLM libraries: HuggingFace Transformers and vLLM.Through rigorous manual analysis, we establish comprehensive taxonomies categorizing bug symptoms into 5 types and root causes into 14 distinct categories.Our primary discovery shows that API misuse has emerged as the predominant root cause (32.17%-48.19%), representing a notable transition from algorithm-focused defects in conventional deep learning frameworks toward interface-oriented problems. Additionally, we examine 7,748 test functions to identify 7 distinct test oracle categories employed in current testing approaches, with predefined expected outputs (such as specific tensors and text strings) being the most common strategy. Our assessment of existing testing effectiveness demonstrates that the majority of bugs escape detection due to inadequate test cases (41.73%), lack of test drivers (32.37%), and weak test oracles (25.90%). Drawing from these findings, we offer some recommendations for enhancing LLM library quality assurance.
format Preprint
id arxiv_https___arxiv_org_abs_2506_12320
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle The Foundation Cracks: A Comprehensive Study on Bugs and Testing Practices in LLM Libraries
Jiang, Weipeng
Zhang, Xiaoyu
Xie, Xiaofei
Yu, Jiongchi
Zhi, Yuhan
Ma, Shiqing
Shen, Chao
Software Engineering
Artificial Intelligence
Large Language Model (LLM) libraries have emerged as the foundational infrastructure powering today's AI revolution, serving as the backbone for LLM deployment, inference optimization, fine-tuning, and production serving across diverse applications. Despite their critical role in the LLM ecosystem, these libraries face frequent quality issues and bugs that threaten the reliability of AI systems built upon them. To address this knowledge gap, we present the first comprehensive empirical investigation into bug characteristics and testing practices in modern LLM libraries. We examine 313 bug-fixing commits extracted across two widely-adopted LLM libraries: HuggingFace Transformers and vLLM.Through rigorous manual analysis, we establish comprehensive taxonomies categorizing bug symptoms into 5 types and root causes into 14 distinct categories.Our primary discovery shows that API misuse has emerged as the predominant root cause (32.17%-48.19%), representing a notable transition from algorithm-focused defects in conventional deep learning frameworks toward interface-oriented problems. Additionally, we examine 7,748 test functions to identify 7 distinct test oracle categories employed in current testing approaches, with predefined expected outputs (such as specific tensors and text strings) being the most common strategy. Our assessment of existing testing effectiveness demonstrates that the majority of bugs escape detection due to inadequate test cases (41.73%), lack of test drivers (32.37%), and weak test oracles (25.90%). Drawing from these findings, we offer some recommendations for enhancing LLM library quality assurance.
title The Foundation Cracks: A Comprehensive Study on Bugs and Testing Practices in LLM Libraries
topic Software Engineering
Artificial Intelligence
url https://arxiv.org/abs/2506.12320