SWE-Tester: Training Open-Source LLMs for Issue Reproduction in Real-World Repositories

Aditya Bharat Soni, Rajat Ghosh, Vaishnavi Bhargava, Valerie Chen, Debojyoti Dutta


Abstract
Software testing is essential for maintaining software reliability, yet issue reproduction tests are often missing when bugs are reported. Automatically generating such tests can accelerate debugging, support test-driven development, and improve automated software engineering systems that rely on execution-based verification. Existing approaches largely depend on proprietary language models, limiting accessibility and reproducibility. We present SWE-Tester a framework for training open-source large language models to generate issue reproduction tests from natural language issue reports. To support this task, we curate a dataset of 41K training instances from 2.6K open-source GitHub repositories. Fine-tuning on this dataset improves issue reproduction performance across multiple model families, yielding gains of up to 10% points in success rate and 21% in change coverage on SWT-Bench Verified. We further study the effects of model size, training data scale, and inference-time compute, observing consistent improvements along all three axes. Our results demonstrate that open-source models can be effectively specialized for issue reproduction test generation and provide a scalable foundation for future software testing and automated issue-resolution systems.
Anthology ID:
2026.emnlp-industry.43
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Pepa Atanasova, Gholamreza Haffari, Minghan Wang
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
720–729
Language:
URL:
https://aclanthology.org/2026.emnlp-industry.43/
DOI:
Bibkey:
Cite (ACL):
Aditya Bharat Soni, Rajat Ghosh, Vaishnavi Bhargava, Valerie Chen, and Debojyoti Dutta. 2026. SWE-Tester: Training Open-Source LLMs for Issue Reproduction in Real-World Repositories. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing: Industry Track, pages 720–729, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SWE-Tester: Training Open-Source LLMs for Issue Reproduction in Real-World Repositories (Soni et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-industry.43.pdf