Rails testing on autopilot: Building an agent that writes what developers won't
Source
mistral.ai
Date
Context
AI-generated tests need to be executed before their quality can be judged. In a Rails testing experiment, Mistral AI reports that only about a third of generated tests passed on their first run. Its AI agentAn AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.Full definition → received failure messages and information about untested lines, then revised the tests until they passed.
Mistral also shows an illustrative test that model-based scoring rated favorably, with an average of 0.75, even though a missing parenthesis prevented it from running. That example explains why a plausible-looking test is insufficient. Running the tests supplies concrete feedback from the software itself, which a model's quality score cannot replace as proof of correctness.
Terms in this piece · Glossary
AI agent — An AI system that doesn't just answer once but works toward a goal in a loop — taking actions, reading the results, and deciding what to do next.
