regression-test-generator

<quick_start> Generate regression test for a bug:

1. Collect bug details: error ID, symptoms, root cause, affected component
2. Detect test framework from project (Jest, Vitest, pytest, Playwright)
3. Generate test file following project patterns
4. Present to user for review: [A] Save [B] Edit [C] Skip
5. Save test to tests/regression/ and update error-log.md

Key principle: Tests should FAIL before the fix is applied (proves bug exists). </quick_start>

Check error-log.md to avoid duplicate tests for same error.

Extract from debug context:

• Error ID: ERR-XXXX from error-log.md (or generate new)
• Title: Brief description (e.g., "Dashboard timeout due to missing pagination")
• Symptoms: Observable behavior (error message, incorrect output)
• Root cause: Why the bug occurred (from 5 Whys analysis)
• Component: Affected file/function (e.g., StudentProgressService.fetchExternalData)
• Reproduction steps: How to trigger the bug

Example:

error_id: ERR-0042
title: Dashboard timeout due to missing pagination
symptoms: Dashboard fails to load, timeout after 30s
root_cause: Missing pagination parameter causes over-fetching
component: src/services/StudentProgressService.ts:fetchExternalData
reproduction:
  - Navigate to /dashboard/student/123
  - Click "Load Data" button
  - Observe timeout error

Check project configuration (in priority order):

1. docs/project/tech-stack.md (if exists):

   grep -i "test\|jest\|vitest\|pytest\|playwright" docs/project/tech-stack.md
   

2. package.json (JavaScript/TypeScript):

   # Check devDependencies
   grep -E '"(jest|vitest|@playwright/test|mocha)"' package.json
   

3. pyproject.toml / requirements.txt (Python):

   grep -E "(pytest|unittest|nose)" pyproject.toml requirements.txt
   

4. Existing test file patterns:

   # JavaScript patterns
   find . -name "*.test.ts" -o -name "*.spec.ts" | head -1
   
   # Python patterns
   find . -name "*_test.py" -o -name "test_*.py" | head -1
   

5. Defaults:

   • JavaScript/TypeScript: Jest
   • Python: pytest
   • Document assumption in test file comment

Output: Framework name and test file extension (e.g., Jest → .test.ts)

Find appropriate location:

1. Check if tests/regression/ exists → use it
2. Check project test structure:
   • tests/ directory → tests/regression/
   • __tests__/ directory → __tests__/regression/
   • Co-located tests (same dir as source) → src/__tests__/regression/
3. Create tests/regression/ if no pattern found

File naming:

• Format: regression-ERR-{ID}-{slug}.{ext}
• Slug: lowercase kebab-case from title
• Examples:
  • regression-ERR-0042-dashboard-timeout.test.ts
  • test_regression_err_0042_dashboard_timeout.py

Use framework-appropriate template from references/framework-templates.md.

Structure (Arrange-Act-Assert):

Header: Error ID, title, description, root cause, link to error-log

describe/class: "Regression: ERR-XXXX - {title_short}"
  test: "should {expected} when {condition}"
    ARRANGE: Set up bug scenario (data, mocks, state)
    ACT: Execute action that caused bug
    ASSERT: Verify correct behavior (would have failed before fix)