# Feature Parity Checklist

Use this checklist to ensure all functionality is preserved during refactoring.

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## Project: [Project Name]
## Refactoring Scope: [Brief description]
## Date: [YYYY-MM-DD]

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## Feature Inventory

### API Endpoints

| Endpoint | Method | Before | After | Verified |
|----------|--------|--------|-------|----------|
| /api/v1/example | GET | Working | | [ ] |
| | | | | [ ] |

### Core Functions

| Function/Module | Purpose | Before | After | Verified |
|-----------------|---------|--------|-------|----------|
| | | Working | | [ ] |
| | | | | [ ] |

### User Workflows

| Workflow | Steps | Before | After | Verified |
|----------|-------|--------|-------|----------|
| User login | 1. Enter credentials 2. Submit | Working | | [ ] |
| | | | | [ ] |

### Integrations

| External System | Integration Type | Before | After | Verified |
|-----------------|------------------|--------|-------|----------|
| | API/Webhook/DB | Working | | [ ] |
| | | | | [ ] |

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## Behavioral Parity

### Input Handling
- [ ] Same inputs produce same outputs
- [ ] Error messages unchanged (or improved)
- [ ] Validation rules preserved
- [ ] Edge cases handled identically

### Output Format
- [ ] Response structure unchanged
- [ ] Data types preserved
- [ ] Null handling consistent
- [ ] Date/time formats preserved

### Side Effects
- [ ] Database writes produce same results
- [ ] File operations unchanged
- [ ] External API calls preserved
- [ ] Event emissions maintained

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## Non-Functional Parity

### Performance
- [ ] Response times within baseline +10%
- [ ] Memory usage within baseline +10%
- [ ] CPU usage within baseline +10%
- [ ] No new N+1 queries introduced

### Security
- [ ] Authentication unchanged
- [ ] Authorization rules preserved
- [ ] Input sanitization maintained
- [ ] No new vulnerabilities introduced

### Reliability
- [ ] Error handling preserved
- [ ] Retry logic maintained
- [ ] Timeout behavior unchanged
- [ ] Circuit breakers preserved

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## Test Coverage

| Test Type | Before | After | Status |
|-----------|--------|-------|--------|
| Unit Tests | X pass | | [ ] Same or better |
| Integration Tests | X pass | | [ ] Same or better |
| E2E Tests | X pass | | [ ] Same or better |

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## Verification Steps

### Automated Verification
1. [ ] All existing tests pass
2. [ ] No new linting errors
3. [ ] Coverage >= baseline

### Manual Verification
1. [ ] Smoke test critical paths
2. [ ] Verify UI behavior (if applicable)
3. [ ] Test error scenarios

### Stakeholder Sign-off
- [ ] QA approved
- [ ] Product owner approved (if behavior changed)

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## Discrepancies Found

| Feature | Expected | Actual | Resolution | Status |
|---------|----------|--------|------------|--------|
| | | | | |

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## Notes
- Any intentional behavior changes must be documented and approved
- Update this checklist as refactoring progresses
- Keep baseline metrics for comparison