Microsoft open-sources unit-test AI agent, beats stock Copilot

Microsoft open-sourced code-testing-generator, a polyglot unit-test agent shipped in the MIT-licensed dotnet/skills repository. It reads a repo to detect language, test framework, and conventions before writing, running, and validating tests, completing 140 of 152 internal benchmark tasks versus 120 for stock GitHub Copilot on the same underlying model.

Why it matters: The gains were concentrated in vague or diff-targeted prompts, suggesting the improvement comes from better repo-context gathering rather than a stronger base model - a reminder that agent scaffolding and tooling can matter as much as the underlying LLM for real coding tasks.