FairTest: Search-Based Fairness Testing for Multi-Agent Reinforcement Learning Systems

2026-09-22

AI Summary

本文提出FairTest，一种基于搜索的测试方法，旨在发现多智能体强化学习系统中的不公平执行问题，通过结合搜索引导与测试优先级策略来实现。

Abstract

Multi-agent Reinforcement Learning (MARL) trains a team of agents that share one environment and learn their policies together. Training maximizes the team return, and a high return does not imply that the rewards are shared fairly among the agents in every episode. Testing is an established way to discover the failures of deep reinforcement learning, yet few methods address the fairness of MARL. In this work, we propose FairTest, a search-based testing approach that seeks the unfair executions of a MARL policy. The design combines search guidance with test prioritization. The guidance scores each candidate with three fitness functions. One measures the fairness of the runs already performed, another predicts the fairness from abstract states and fairness features, and the third reads the decision uncertainty from the policy. Crossover and mutation derive further candidates from the observed executions. The prioritization ranks the candidates by the predicted fairness and the decision uncertainty, so that the runs reach the candidates where failures are expected. FairTest is evaluated on three environments and two MARL algorithms, and four baselines are given the same budget. It detects the most fairness failures compared to three baselines with statistical significance and large effect sizes. The failure count exceeds that of the strongest baseline by 221% on average and coverage improves by an average of 23%.

Problem

• Multi-agent Reinforcement Learning
• fairness
• testing

Innovation

• search-based testing
• fairness in MARL
• test prioritization