Skip to content
Preprint

SWE-NFI: Studying and Benchmarking Coding Agents for Non-Functional Improvements

Jul 2026 · 0 citations · 76 references
Computer Science

TL;DR

This paper operationalizes developer-oriented NFIs into 92 executable rules and develops a comprehensive evaluation suite that combines functional correctness testing with rule-based NFI evaluation, and evaluates state-of-the-art commercial and open-source coding agents.

Abstract

Although coding agents have achieved impressive performance on correctness-oriented benchmarks, their ability to make behavior-preserving non-functional improvements (NFIs) remains underexplored. In real-world software development, developers continuously improve software quality without changing observable behavior, yet existing benchmarks primarily evaluate functional correctness and provide limited support for assessing these non-functional improvements. In this paper, we present SWE-NFI, a benchmark for evaluating coding agents on NFIs beyond functional correctness. Our benchmark contains 188 tasks constructed from real merged pull requests in open-source Python projects. We operationalize developer-oriented NFIs into 92 executable rules and develop a comprehensive evaluation suite that combines functional correctness testing with rule-based NFI evaluation. We evaluate state-of-the-art commercial and open-source coding agents. Although the best-performing agent achieves a 70.0\% functional correctness rate, all evaluated agents generally fall short of human developers in overall NFI capability. The gap is particularly evident for structural code improvements, where agents'NFI scores range from 0.0 to 1.3, compared with 1.5 for the human reference. Our benchmark and findings provide a reproducible foundation for evaluating and advancing coding agents beyond functional correctness.

View source

Similar papers

Jul 2026

ICAE-Bench: Evaluating Coding Agents as Interactive Project Builders

ICAE-Bench, a benchmark for evaluating coding agents under interactive project-building settings, starts from a fuzzy product requirement, simulating the dynamic paradigm with an automated User Agent, and introduces three key designs.

Zhongyuan Peng, Dan Huang, Chuyu Zhang et al. · 3 citations · ⚡1
Jul 2026

A Multi-Agent Benchmarking Framework for Evaluating the Performance of Large Language Models in Logic Programming

A configurable multi-agent framework for benchmarking LLMs in Prolog code generation that combines a Code Generator Agent, a deterministic execution layer using SWI-Prolog, and an evaluator based on the LLM-as-a-Judge paradigm that supports model-agnostic experimentation and evaluates outputs across functional correctness, efficiency, structural properties and evaluator reliability.

Nikolaos Karamousalidis, P. Kefalas · 0 citations

AI-Generated Code Is Not Reproducible (Yet): An Empirical Study of Execution Reliability in LLM-Based Coding Agents

An empirical study of whether complete software artifacts generated by LLM coding agents can be executed in a clean environment using only the code, dependency specifications, and instructions the agent provides suggests that coding-agent evaluation should treat clean-environment executability as a first-class metric alongside functional correctness.

Bhanu Prakash Vangala, Ashish Gehani, Tanu Malik · 0 citations
#software testing Preprint Aug 2026

SWE Refactor Bench: Can Coding Agents Complete a Long-Horizon, Whole-Repository Stack Migration?

SWE Refactor Bench is introduced, a benchmark comprising 20 whole-repository migrations, covering 4 kinds of technical debt, and SWE Refactor Bench is positioned as a rigorous testbed for developing coding agents for reliable whole-repository migrations.

Deyao Hong, Y. Chi, Wenyi Li et al. · 0 citations
#artificial intelligence Review Sep 2026

SWE-Gate: Passing Functional Tests Is Not Enough for Software Engineering Agents

Repository-level software engineering benchmarks have significantly advanced the evaluation of coding agents, but existing benchmarks primarily measure whether generated patches pass functional tests and overlook review-derived acceptance constraints (review constraints) that often influence whether a patch is acceptable in real-world software development. We introduce SWE-Gate, a repository-level benchmark for software engineering agents that explicitly evaluates review constraint compliance alongside functional correctness. SWE-Gate derives review constraints from real pull request review comments and synthesizes repository-level repair instances around these constraints. Each instance provides separate functional and constraint tests, together with non-compliant and gold patches, enabling explicit separation between issue resolution capability and review constraint compliance. We construct SWE-Gate with 303 repository-level repair instances spanning 75 open-source Python repositories across diverse software domains. Experiments with four LLM backends spanning different capability levels under a common coding-agent scaffold reveal a substantial gap between functional success and success under the complete repair specification: among 644 repairs that pass the functional tests, 221 fail to satisfy the provided review constraints. These findings show that functional-only evaluation overestimates agents'ability to satisfy the full requirements of repository-level repair tasks. The replication package including code, data, and experimental results is available at https://github.com/DeepSoftwareAnalytics/SWE-Gate.

Xin He, Yan-Lin Wang, Ming-Wei Liu et al. · 0 citations
Conference Jul 2026

MASTEST: A LLM-Based Multi-Agent System For Testing RESTful APIs

Testing RESTful API is increasingly complicated but indispensable to quality assurance of cloud-native applications. This paper reports a multi-agent system called MASTEST that combines LLM-based intelligent agents and programmed agents to automate REST API testing. They form a complete tool chain covering the whole workflow of REST API test with API specification in the OpenAPI Swagger format as the input. It also incorporates human testers in the process to review and correct LLM generated test artefacts to control the quality of testing activities. MASTEST is evaluated on two LLMs, GPT-4o and DeepSeek V3.1 Reasoner with five public APIs. Its performances on various testing activities are measured by a wide range of metrics, including adequacy and coverage metrics, the syntax and data type correctness of generated test scripts, the usability of LLM generated test cases and scripts, as well as the bug detection ability. Experiment results demonstrated that both DeepSeek and GPT-4o achieved a high overall performance but had strengths and weaknesses on different testing activities. MASTEST generated test cases achieved 94% and 98% unit test coverage and 79% and 78% system test coverage for GPT-4o and DeepSeek respectively in comparison with human designed test cases. The generated test scripts maintained 100% syntax correctness and only required minimal manual edits for semantic correctness. The generated test scripts contain assertions on the expected status code as well as contents in the response messages. They are highly capable of detecting bugs in the REST APIs. Experiment data shows that the bug detection rates are between 2.13 to 4.50 per operation. These findings indicate that MASTEST is highly efficient and effective.

Xiaoke Han, Hong Zhu · 1 citation · ⚡1

We use cookies to run the site and, with your consent, for analytics and to show ads. See our Cookie Policy.