Co-Evolving LLM Coder and Unit Tester via Reinforcement Learning

Yinjie Wang, Ling Yang, tyfeld, shenke, Mengdi Wang

Co-Evolving LLM Coder and Unit Tester via Reinforcement Learning: 25 upvotes on Hugging Face Daily Papers, #15 of 50 papers on 2025-06-04. Day-by-day upvote history.

We propose CURE, a novel reinforcement learning framework with a dedicated reward design that co-evolves coding and unit test generation capabilities based on their interaction outcomes, without any ground-truth code as supervision. This approach enables flexible and scalable training and allows the unit tester to learn directly from the coder's mistakes. Our derived ReasonFlux-Coder-7B and 14B models improve code generation accuracy by 5.3% and Best-of-N accuracy by 9.0% after optimization on Qwen2.5-Instruct models, outperforming similarly sized Qwen-Coder, DeepSeek-Coder, and Seed-Coder. They naturally extend to downstream tasks such as test-time scaling and agentic coding-achieving a 8.1% improvement over the base model. For the long-CoT model, our ReasonFlux-Coder-4B consistently outperforms Qwen3-4B while achieving 64.8% inference efficiency in unit test generation. Notably, we also find that our model can serve as an effective reward model for reinforcement learning on base models. Project: https://github.com/Gen-Verse/CURE

Paper page on Hugging Face · arXiv

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