RESTifAI: LLM-Based Workflow for Reusable REST API Testing

TL;DR

RESTifAI addresses robust REST API testing by automatically generating reusable, CI/CD-ready test suites that cover both successful (2xx) and invalid (4xx) inputs. It introduces a modular, LLM-driven workflow—Happy Path Generation, Negative Value Generator, and Test Case Builder—that ingests OpenAPI specifications to produce executable tests. The approach demonstrates competitive performance against AutoRestTest and LogiAgent on multiple services, achieving high operation coverage and producing targeted test cases with reduced token usage. The work highlights practical industrial applicability, while noting limitations in assertions for business logic and proposing future enhancements including human-in-the-loop strategies.

Abstract

With this paper, we introduce RESTifAI, an LLM-driven approach for generating reusable, CI/CD ready REST API tests, following the happy-path approach. Unlike existing tools that often focus primarily on internal server errors, RESTifAI systematically constructs valid test scenarios (happy paths) and derives negative cases to verify both intended functionality (2xx responses) and robustness against invalid inputs or business-rule violations (4xx responses). The results indicate that RESTifAI performs on par with the latest LLM tools, i.e., AutoRestTest and LogiAgent, while addressing limitations related to reusability, oracle complexity, and integration. To support this, we provide common comparative results and demonstrate the tool's applicability in industrial services. For tool demonstration, please refer to https://www.youtube.com/watch?v=2vtQo0T0Lo4. RESTifAI is publicly available at https://github.com/casablancahotelsoftware/RESTifAI.

Figures (1)

• Figure 1: RESTifAI workflow with illustrative outputs from four intermediate steps. , , are structured LLM outputs.