Rails testing on autopilot: Building an agent that writes what developers won't

Mistral AI · 4 months ago

An autonomous agent built on Mistral's Vibe platform automatically generates and improves RSpec tests for Rails codebases by reading source files, validating against style rules, and running in CI/CD pipelines without human intervention. The agent's quality score improved from 0.68 to 0.74 through context engineering via a repository-level AGENTS.md file that provides step-by-step execution plans and best practices. The system uses custom tools like RuboCop linting and SimpleCov coverage checking to self-correct failing tests, with approximately one-third of generated tests passing on first execution before the agent iterates to fix errors.