reproduce-bug

name	reproduce-bug
description	Systematically reproduce a bug from a ticket or report with a failing regression test, using a structured hypothesis-driven methodology.
license	Sustainable Use License 1.0
metadata	{"domain":"devops","subdomain":"testing","tags":"debugging, bug-reproduction, regression-test, tdd","author":"Yunseo Kim <[e-mail]>","lastUpdated":"12026-02-26","provenance":"adapted"}

Bug Reproduction Framework

Given a bug report or ticket context ($ARGUMENTS), systematically reproduce the bug with a failing regression test.

Step 1: Parse Signals

Extract the following from the provided ticket/report context:

• Error message / stack trace (if provided)
• Reproduction steps (if provided)
• Sample data or configuration (if attached)
• Affected area (module, component, service, API, etc.)
• Version where it broke / last working version

Step 2: Route to Test Strategy

Based on the affected area, pick the appropriate test layer and pattern:

Area	Test Layer	Approach
Business logic / service	Unit test	Mock dependencies, test pure logic
API endpoint	Integration test	HTTP client + test server
Database operation	Integration test	Test database + fixtures
UI component	Component test	Render + simulate interaction
CLI command	Integration test	Spawn process + assert output
Configuration	Unit test	Load config + validate values
End-to-end flow	E2E test	Full stack + browser/client automation

Adapt the test layer to your project's testing infrastructure. Look for existing test patterns in the codebase and follow them.

Step 3: Locate Source Files

Find the source code for the affected area:

1. Search for the module/service/component mentioned in the report
2. Find shared utility files (common location for bugs)
3. Check for existing test files in the same area
4. Look at recent git history on affected files (git log --oneline -10 -- <path>)

Step 4: Trace the Code Path

Read the source code and trace the execution path that triggers the bug:

• Follow the call chain from entry point to the failure
• Identify the specific line(s) where the bug manifests
• Note any error handling (or lack thereof) around the bug

Step 5: Form Hypothesis

State a clear, testable hypothesis:

• "When [input/condition], the code does [wrong thing] because [root cause]"
• Identify the exact line(s) that need to change
• Predict what the test output will show

Step 6: Find Test Patterns

Look for existing tests in the same area:

1. Check test/ or __tests__/ directories near the affected code
2. Identify which mock/setup patterns they use
3. Use the same patterns for consistency
4. If no tests exist, find the closest similar module's tests as a template

Step 7: Write Failing Test

Write a regression test that:

• Uses the patterns found in Step 6
• Targets the specific hypothesis from Step 5
• Includes a comment referencing the ticket/issue ID
• Asserts the CORRECT behavior (test will fail on current code)
• Also includes a "happy path" test to prove the setup works

Step 8: Run and Score

Run the test using the project's test runner.

Classify the result:

Confidence	Criteria	Output
CONFIRMED	Test fails consistently, failure matches hypothesis	Reproduction Report
LIKELY	Test fails but failure mode differs slightly	Report + caveat
UNCONFIRMED	Cannot trigger the failure	Report: what was tried
SKIPPED	Hit a hard bailout trigger	Report: why skipped
ALREADY_FIXED	Bug no longer reproduces on current code	Report: when fixed

Step 9: Iterate or Bail

If UNCONFIRMED after first attempt:

• Revisit hypothesis -- re-read the code path
• Try a different test approach or layer
• Maximum 3 attempts before declaring UNCONFIRMED

Hard bailout triggers (stop immediately):

• Requires real third-party API credentials
• Race condition / timing-dependent
• Requires specific cloud/enterprise infrastructure
• Requires manual UI interaction that cannot be scripted

Output: Reproduction Report

Present findings in this format:

---

Ticket: [ID] -- [title] Confidence: [CONFIRMED | LIKELY | UNCONFIRMED | SKIPPED | ALREADY_FIXED]

Root Cause

[1-2 sentences explaining the bug mechanism]

Location

File	Lines	Issue
path/to/file	XX-YY	Description of the problem

Failing Test

path/to/test/file -- X/Y tests fail:

1. test name -- [failure description]

Fix Hint

[Pseudocode or description of the fix approach]

---

Important

• DO NOT fix the bug -- only reproduce it with a failing test
• Leave test files in place as evidence (don't commit unless asked)
• Always redirect build output: command > build.log 2>&1
• DO NOT look at existing fix PRs -- the goal is to reproduce from signals alone