Repro Surgeon

Keep the failure.
Shrink the project.

A bug report needs something another developer can run. Repro Surgeon tests smaller versions of a failing npm app, then exports a project with its own verifier.

Follow a real reduction

A recorded run of the bundled rounding example. No code is uploaded or executed in this page.

The application fails

Expected failure

The check catches a rounding error: line totals must round only once.

Loading the recorded evidence…

Actual baseline output excerpt.

Source remaining

—
—source bytes

    Loading recording.

    Inspect the full interactive report

    Run it yourself

    One command runs the real example, reduction, and fresh verification. Requires Node 22.18+ and npm 10+ on Linux or macOS.

    Checks start in temporary copies with your process permissions. They can still access other files. Execution boundary and container setup.

    npx repro-surgeon demo --out ./rounding-repro

    Choose a new output directory. Open its report.html when the command finishes.

    Take the reproduction with you

    The recorded export includes the reduced application, a locked dependency manifest, an integrity record, and a verifier that runs without Repro Surgeon installed.

    Download the verified exampleSHA-256 checksum
    tar -xzf rounding-repro.tar.gz
cd rounding-repro
node .repro/verify.mjs

    This is an authored demonstration, not a general benchmark. Every accepted change had two matching executions; the baseline and export each had three. The verifier succeeds when the application's expected failure occurs.