Repair-R1: Better Test Before Repair
Authors: name: Haichuan Hu, name: Xiaochen Xie, name: Quanjun Zhang

APR (Automated Program Repair) aims to automatically locate program defects,
generate patches and validate the repairs. Existing techniques for APR are
often combined with LLMs (Large Language Models), which leverages the
code-related knowledge of LLMs to improve repair effectiveness. Current
LLM-based APR methods typically utilize test cases only during the inference
stage, adopting an iterative approach that performs repair first and validates
it through test execution afterward. This conventional paradigm neglects two
important aspects: the potential contribution of test cases in the training
phase, and the possibility of leveraging testing prior to repair. To address
this, we propose Repair-R1, which introduces test cases into the model's
training phase and shifts test generation to precede repair. The model is
required to first generate discriminative test cases that can distinguish
defective behaviors, and then perform repair based on these tests. This enables
the model to better locate defects and understand the underlying causes of
defects, thereby improving repair effectiveness. We implement Repair-R1 with
three different backbone models, using RL (reinforcement learning) to
co-optimize test generation and bug repair. Experimental results on four widely
adopted benchmarks demonstrate the superiority of Repair-R1. Specially,
compared to vanilla models, Repair-R1 improves repair success rate by 2.68\% to
48.29\%, test generation success rate by 16.38\% to 53.28\%, and test coverage
by 0.78\% to 53.96\%. We publish the code and weights at
https://github.com/Tomsawyerhu/APR-RL and
https://huggingface.co/tomhu/Qwen3-4B-RL-5000-step.