Coverage Analyzer Skill

Purpose

Analyzes project test coverage and identifies areas lacking tests. Recommends code to test with priority.

When to Use

• Coverage analysis requests
• Finding untested files
• Coverage improvement guidance
• Verifying critical code test status

Workflow

Step 1: Check Coverage Status

Analyzing test environment...

**Test Runner**: Jest
**Test Files**: 45
**Coverage Report**: coverage/lcov-report/
**Current Coverage**: 68%

Step 2: Select Analysis Type

AskUserQuestion:

"What coverage analysis do you need?"
Options:
- Overall coverage status
- Find untested files
- Low coverage files
- Critical code test status
- Coverage improvement priorities

Analysis Types

Untested File Detection

Targets:
- src/**/*.ts
- src/**/*.tsx
- lib/**/*.ts

Excluded:
- *.d.ts (type definitions)
- *.test.ts (test files)
- index.ts (barrel files)
- *.config.ts (config files)

Results Format:

## Untested Files (15)

### High Priority (Business Logic)
| File | Lines | Complexity | Recommendation |
|------|-------|------------|----------------|
| src/utils/payment.ts | 120 | HIGH | Needs immediate tests |
| src/services/auth.ts | 85 | HIGH | Needs immediate tests |

### Medium Priority (Utilities)
| File | Lines | Complexity | Recommendation |
|------|-------|------------|----------------|
| src/utils/format.ts | 45 | MEDIUM | Tests recommended |

### Low Priority (Simple Code)
| File | Lines | Complexity | Recommendation |
|------|-------|------------|----------------|
| src/constants/index.ts | 20 | LOW | Optional |

Coverage Metrics

Metric	Description	Target
Line Coverage	Executed lines ratio	> 80%
Branch Coverage	Executed branches ratio	> 75%
Function Coverage	Executed functions ratio	> 85%
Statement Coverage	Executed statements ratio	> 80%

Analysis Results:

### Overall Status
| Metric | Current | Target | Status |
|--------|---------|--------|--------|
| Lines | 68% | 80% | WARNING |
| Branches | 55% | 75% | CRITICAL |
| Functions | 72% | 85% | WARNING |

### Low Coverage Files (< 50%)
| File | Lines | Branches | Impact |
|------|-------|----------|--------|
| src/services/payment.ts | 23% | 10% | HIGH |
| src/components/Form.tsx | 45% | 30% | MEDIUM |

Critical Code Analysis

Priority Criteria:

Criteria	Description	Weight
Business Logic	Payment, auth, data processing	HIGH
Usage Frequency	Import count	MEDIUM
Complexity	Cyclomatic Complexity	MEDIUM
Change Frequency	git log based	LOW

### CRITICAL (Must Test)
| File | Importance | Coverage | Recommendation |
|------|------------|----------|----------------|
| src/services/payment.ts | CRITICAL | 23% | Add tests immediately |
| src/utils/auth.ts | CRITICAL | 0% | Create test file |

### HIGH (Should Test)
| File | Importance | Coverage | Recommendation |
|------|------------|----------|----------------|
| src/hooks/useCart.ts | HIGH | 45% | Add edge cases |

Improvement Priorities

## Coverage Improvement Priorities

### Priority 1: High Importance + Low Coverage
Needs immediate tests

| File | Current | Expected Gain | Effort |
|------|---------|---------------|--------|
| src/services/payment.ts | 23% | +57% → 80% | 3 hours |
| src/utils/auth.ts | 0% | +80% → 80% | 2 hours |

### Priority 2: High Usage Frequency
Frequently used utilities

| File | Current | Imports | Effort |
|------|---------|---------|--------|
| src/utils/format.ts | 45% | 32 | 1 hour |
| src/hooks/useApi.ts | 60% | 28 | 1 hour |

### Priority 3: High Complexity
Bug-prone code

| File | Current | Complexity | Effort |
|------|---------|------------|--------|
| src/components/Form.tsx | 45% | 15 | 2 hours |

### Expected Results
Current: 68%
After Priority 1: 75%
After Priority 2: 80%
After Priority 3: 85%

Response Template

## Test Coverage Analysis Results

**Project**: [name]

### Overall Status
| Metric | Current | Target | Gap |
|--------|---------|--------|-----|
| Lines | 68% | 80% | -12% |
| Branches | 55% | 75% | -20% |
| Functions | 72% | 85% | -13% |

### Untested Critical Files (5)
1. `src/services/payment.ts` - Payment logic (CRITICAL)
2. `src/utils/auth.ts` - Auth utilities (HIGH)
3. `src/hooks/useCart.ts` - Cart hook (HIGH)

### Low Coverage Files (< 50%)
1. `src/components/CheckoutForm.tsx` - 45%
2. `src/services/api.ts` - 38%

### Recommended Actions
1. [ ] Add payment.ts unit tests (expected +5% overall)
2. [ ] Create auth.ts test file (expected +3% overall)
3. [ ] Improve CheckoutForm component tests

### Next Steps
Use `test-generator` skill to auto-generate tests for these files.

Best Practices

1. Meaningful Coverage: Focus on critical code, not just numbers
2. Gradual Improvement: Don't aim for 100% at once
3. Branch Coverage: More important than line coverage
4. Test Quality: Avoid meaningless tests just for coverage
5. CI Integration: Fail build on coverage decrease

Integration

• test-generator skill: Auto-generate missing tests
• code-reviewer skill: Test quality review
• /generate-tests command: Execute test generation

Notes

• Uses coverage report files (lcov, coverage.json) if available
• Estimates based on file analysis if no report
• 100% coverage is not the goal, focus on critical code