Fault localization for reinforcement learning

Reinforcement Learning is widely adopted in industry to approach control tasks in intelligent way. The quality of these programs is important especially when they are used for critical tasks like autonomous driving. Testing and debugging these programs are complex because they behave autonomously without providing insights about the reasons of the decisions taken. Even these decisions could be wrong if they learned from faults. In this paper, we present the first approach to automatically locate faults in Reinforcement Learning programs. This approach called SBFL4RL analyses several executions to extract those internal states that commonly reduce the performance of the program when they are covered. Locating these states can help testers to understand a known fault, or even detect an unknown fault. SBFL4RL is validated in 2 case studies locating correctly an injected fault. Initial results suggest that the faults of reinforcement learning programs can be automatically located, and there is room for further research.