ABOUTCODEX / DEVELOPER CODEX PATH

Reproduce, fix, and verify a bug

Use a failing reading-list example to practise a complete debugging loop.

Before you begin

Python 3.10+ and a disposable folder. Basic familiarity with running commands.

Suggested practice: 30–45 minutes. Work at your own pace; this is an editorial estimate.

Download the practice project · Read the companion skill

  1. 01

    Reproduce the symptom

    Read: Codex debugging skills: reproduce, trace, fix, and verify

    Try it: Run the starter tests and record the duplicate-save failure.

    Check your result: The test fails for the expected reason; record command and output.

  2. 02

    Trace the cause and make a small fix

    Read: A dependable workflow for Codex-assisted changes

    Try it: Find why repeated saves append the same ID. Preserve order and avoid input mutation.

    Check your result: Explain how the changed condition addresses the demonstrated failure.

  3. 03

    Verify the patch and its limits

    Read: Review code with Codex: a practical checklist

    Try it: Run the same tests after the fix; review blank, empty, and repeated inputs.

    Check your result: All six tests pass. Your handoff states the tested Python version and remaining limits.

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