CodeContests+: High-Quality Test Case Generation for Competitive
  Programming
Authors: name: Zihan Wang; name: Siyao Liu; name: Yang Sun; name: Hongyan Li; name: Kai Shen
Published: 2025-06-06 07:29:01

Abstract: Competitive programming, due to its high reasoning difficulty and precise
correctness feedback, has become a key task for both training and evaluating
the reasoning capabilities of large language models (LLMs). However, while a
large amount of public problem data, such as problem statements and solutions,
is available, the test cases of these problems are often difficult to obtain.
Therefore, test case generation is a necessary task for building large-scale
datasets, and the quality of the test cases directly determines the accuracy of
the evaluation. In this paper, we introduce an LLM-based agent system that
creates high-quality test cases for competitive programming problems. We apply
this system to the CodeContests dataset and propose a new version with improved
test cases, named CodeContests+. We evaluated the quality of test cases in
CodeContestsPlus. First, we used 1.72 million submissions with pass/fail labels
to examine the accuracy of these test cases in evaluation. The results
indicated that CodeContests+ achieves significantly higher accuracy than
CodeContests, particularly with a notably higher True Positive Rate (TPR).
Subsequently, our experiments in LLM Reinforcement Learning (RL) further
confirmed that improvements in test case quality yield considerable advantages
for RL.