AutoMT: A Multi-Agent LLM Framework for Automated Metamorphic Testing of Autonomous Driving Systems
Linfeng Liang, Chenkai Tan, Yao Deng, Yingfeng Cai, T. Y Chen, Xi Zheng
TL;DR
AutoMT addresses the oracle problem in autonomous driving testing by automating metamorphic testing through a multi-agent LLM framework. It automatically extracts metamorphic relations from local traffic rules, grounds them in a RAG-based MR repository, analyzes real-world test cases with a vision-language agent, and generates valid follow-up scenarios via image editing and video synthesis. The approach yields greater MR diversity, higher validation rates, and improved detection of behavioral safety violations compared to expert-defined baselines, highlighting its practical impact for industrial ADS testing. The modular, ontology-driven pipeline is readily integrable into existing pipelines and can be extended to simulation-based testing to systematically cover underrepresented or safety-critical scenarios.
Abstract
Autonomous Driving Systems (ADS) are safety-critical, where failures can be severe. While Metamorphic Testing (MT) is effective for fault detection in ADS, existing methods rely heavily on manual effort and lack automation. We present AutoMT, a multi-agent MT framework powered by Large Language Models (LLMs) that automates the extraction of Metamorphic Relations (MRs) from local traffic rules and the generation of valid follow-up test cases. AutoMT leverages LLMs to extract MRs from traffic rules in Gherkin syntax using a predefined ontology. A vision-language agent analyzes scenarios, and a search agent retrieves suitable MRs from a RAG-based database to generate follow-up cases via computer vision. Experiments show that AutoMT achieves up to 5 x higher test diversity in follow-up case generation compared to the best baseline (manual expert-defined MRs) in terms of validation rate, and detects up to 20.55% more behavioral violations. While manual MT relies on a fixed set of predefined rules, AutoMT automatically extracts diverse metamorphic relations that augment real-world datasets and help uncover corner cases often missed during in-field testing and data collection. Its modular architecture separating MR extraction, filtering, and test generation supports integration into industrial pipelines and potentially enables simulation-based testing to systematically cover underrepresented or safety-critical scenarios.
