regression-test-generator

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)

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)

=== Regression Test Generated ===

Error: ERR-0042 - Dashboard Timeout Due to Missing Pagination

File: tests/regression/regression-ERR-0042-dashboard-timeout.test.ts

--- Generated Test Code ---
[Full test code here]
---

This test will:
- {describe what test validates}
- {explain why test would have failed before fix}

What would you like to do?
  [A] Save test and continue
  [B] Edit test before saving
  [C] Skip generation (add to debt tracker)

>

**Regression Test**:
- **File**: `tests/regression/regression-ERR-0042-dashboard-timeout.test.ts`
- **Status**: Generated
- **Validates**: Pagination parameter prevents timeout

// BAD: Tests internal method name
test('calls _fetchWithPagination', () => {
  expect(service._fetchWithPagination).toHaveBeenCalled();
});

// GOOD: Tests behavior user expects
test('should return paginated results within 5 seconds', async () => {
  const result = await service.fetchData(studentId);
  expect(result.length).toBeLessThanOrEqual(10);
});

// BAD: Breaks if CSS class changes
await page.locator('.btn-primary-xl-dashboard').click();

// GOOD: Stable, user-focused
await page.getByRole('button', { name: 'Load Data' }).click();

// BAD: No reference to error-log.md
test('dashboard loads', () => { /* ... */ });

/**
 * Regression Test for ERR-0042
 * @see specs/my-feature/error-log.md#ERR-0042
 */
test('should load dashboard within 5s (ERR-0042)', () => { /* ... */ });

// Include: State that triggers bug
const service = new StudentProgressService();
const result = await service.fetchData(studentWithLargeDataset);

// Exclude: Unrelated setup
// const userPrefs = loadPreferences(); // Not needed for this test

// BAD: Vague assertion
expect(result).toBeTruthy();

// GOOD: Specific to bug being prevented
expect(result.length).toBeLessThanOrEqual(10); // Pagination limit
expect(response.time).toBeLessThan(5000); // No timeout

/**
 * Regression Test for ERR-0042: Dashboard Timeout
 *
 * Bug: Dashboard failed to load due to missing pagination
 * Root Cause: API call fetched all records (1000+) instead of paginated (10)
 * Fixed: Added page_size parameter to API call
 *
 * @see specs/001-dashboard/error-log.md#ERR-0042
 */