From Failing Tests to Fix PRs in One Command (GitHub Copilot CLI Challenge)

Source: Dev.to

Overview

This submission for the GitHub Copilot CLI Challenge introduces copilot‑bugfix, a GitHub Copilot CLI‑powered agent that takes you from a red test to a ready‑to‑review pull request with a single command. Instead of manually reading stack traces, hunting through files, and hand‑crafting patches, you simply run the tool and let it handle the rest.

How It Works

1. Run the command – the tool executes your test suite and captures the full failure output.
2. Build a debug bundle – it gathers a rich context bundle that includes the stack trace, recent diffs, and relevant file snippets.
3. Ask Copilot – the bundle is sent to gh copilot suggest, which explains the root cause and proposes a unified‑diff patch.
4. Review & apply – the suggested patch is displayed; on confirmation it is applied and the tests are re‑run.
5. Optional PR creation – the tool can create a new branch, generate a conventional commit message with Copilot, and open a PR via the GitHub CLI.

Usage

copilot-bugfix "npm test -- failing-test"

Running the command produces step‑by‑step terminal output:

• test execution → context bundle creation → Copilot analysis → patch preview
• patch application → test re‑run (green)

If the patch is accepted, the tool can automatically:

• create a new branch
• generate a short, conventional commit message (e.g., fix: resolve failing test in XYZ)
• open a pull request with the diff attached

Features

• Automated debugging – captures test output, recent changes, and targeted code snippets.
• AI‑driven analysis – leverages GitHub Copilot CLI to explain failures and suggest fixes.
• Patch preview & safety – displays the diff before applying; a hardened parser validates fenced diffs and hunk‑only patches.
• Commit automation – generates conventional commit messages that read like a teammate’s contribution.
• One‑click PR – optionally creates a branch and opens a PR via gh pr create.

Implementation Details

Analysis & Patch Generation

A curated context bundle is sent to gh copilot suggest. The bundle contains just enough signal (test output, recent git changes, focused snippets) for Copilot to reason about the failure without overwhelming it with the entire repository.

Commit Messages

After a patch is applied, Copilot CLI is invoked again to produce a concise, conventional commit message that follows the project’s commit style.

Safety & Diagnostics

The tool parses Copilot’s output with a hardened parser that understands both fenced diffs and hunk‑only patches. Raw Copilot output can be saved for debugging when something looks off.

Production‑Ready Investments

• Full test coverage – unit tests for the parser (including edge‑case diff formats), integration tests that simulate Copilot output and apply patches, and cross‑platform end‑to‑end tests that mock gh to validate the entire CLI flow.
• Multi‑version CI – GitHub Actions runs the test suite on Node 16, 18, and 20, ensuring green checks for all supported runtimes.
• Repo hygiene – includes CODEOWNERS, CONTRIBUTING, a CI badge, and clear npm scripts (test, test:unit, test:integration, test:e2e).

Testing & CI

The GitHub Actions workflow runs a matrix of:

• Node versions: 16, 18, 20
• Test suites: unit, integration, end‑to‑end

All checks must pass before the repository can be cloned and used.

Repository

copilot‑bugfix on GitHub

Acknowledgements

Thank you to the DEV Community and GitHub for creating the Copilot CLI Challenge. This hackathon inspired a deeper exploration of how AI agents can solve real developer problems—turning a simple “failing test” into a complete “bug → fix → PR” workflow with minimal friction.