Rails Testing on Autopilot: Building an Agent That Writes What Developers Won't

An autonomous agent was built to automatically write RSpec tests for large Ruby on Rails applications, addressing the common issue of untested code. The agent, based on Mistral's Vibe coding assistant, uses a multi-faceted approach involving context engineering, specialized skills, and custom tools. It follows a detailed execution plan from an `AGENTS.md` file and uses specific skill files tailored to different Rails components like models and controllers. To ensure quality, the agent integrates custom tools for RuboCop linting and SimpleCov test coverage, enabling it to validate its generated code and self-correct based on the results. This system runs within a CI/CD pipeline to improve test coverage without human intervention.