Coverage Analyzer

Automatically analyze test coverage and identify untested code.

Philosophy

Knowing what's tested gives confidence to refactor and prevents regressions.

Core Beliefs

1. Visibility Drives Action: Can't improve what you can't measure
2. Not All Code Needs 100% Coverage: Prioritize critical paths over getters/setters
3. Coverage ≠ Quality: 100% coverage doesn't guarantee bug-free code
4. Gap Analysis Guides Testing: Knowing what's untested helps prioritize test writing

Why Coverage Analysis Matters

• Identify Risks: Find critical code without test protection
• Prioritize Effort: Focus testing where it matters most
• Prevent Regressions: Tests catch bugs before they reach users
• Enable Refactoring: Good coverage allows confident code changes

When to Use This Skill

Activate this skill when the user:

• Asks "what code isn't tested?"
• Mentions "test coverage" or "coverage report"
• Says "which tests are missing?"
• Shows code and asks "is this tested?"
• References "untested code paths"
• Asks "what's my coverage percentage?"

Decision Framework

Before analyzing coverage, consider:

What's the Goal?

1. Find coverage gaps → Identify untested code
2. Measure current coverage → Run coverage tools and report percentages
3. Prioritize testing → Focus on critical paths first
4. Improve coverage → Recommend specific tests to write

What's the Scope?

• Specific file - User shows code → Analyze that file's coverage
• Component/module - User mentions feature → Check component tests
• Recent changes - User says "my code" → Check coverage of git diff
• Entire project - User says "overall coverage" → Run project-wide analysis

What Test Types Exist?

Check for:

• PHPUnit tests (PHP) → Run phpunit --coverage-text
• Jest tests (JavaScript) → Run jest --coverage
• Cypress tests (E2E) → Integration coverage only
• Manual test documentation → Note gaps

What Coverage Metrics Matter?

Primary metrics:

• Line coverage - Percentage of lines executed
• Branch coverage - Percentage of decision branches taken
• Function coverage - Percentage of functions called

Priority order:

1. Critical paths (auth, payments, data writes)
2. Public APIs
3. Security-sensitive code
4. Business logic
5. Getters/setters (lowest priority)

What's a Good Target?

• Critical code - Aim for 90%+ coverage
• Business logic - Aim for 80%+ coverage
• Overall project - Aim for 70%+ coverage
• Getters/setters - Can skip, focus on behavior

Decision Tree

User asks about coverage
    ↓
Determine scope (file/component/project)
    ↓
Check for existing test files
    ↓
Run coverage tool (PHPUnit/Jest/Cypress)
    ↓
Analyze gaps (prioritize critical paths)
    ↓
Report coverage with recommendations
    ↓
Suggest specific tests for gaps

Quick Coverage Analysis

1. Check if Tests Exist

PHP (PHPUnit):

# Check for test files
find tests/ -name "*Test.php"

# Check specific class
test -f "tests/src/Unit/DataProcessorTest.php" && echo "Tests exist"

JavaScript (Jest):

# Check for test files
find . -name "*.test.js" -o -name "*.spec.js"

2. Run Coverage Analysis

PHP:

# Generate coverage report
vendor/bin/phpunit --coverage-text

# For Kanopi projects
ddev exec vendor/bin/phpunit --coverage-text

JavaScript:

# Jest coverage
npm run test -- --coverage

# Or directly
npx jest --coverage

3. Identify Gaps

Common untested areas:

• Error handling (catch blocks)
• Edge cases (empty input, null values)
• Private methods (test via public interface)
• Complex conditionals
• New features without tests

Response Format

## Test Coverage Analysis

### Summary
- **Overall Coverage**: 72%
- **Files Analyzed**: 45
- **Tested**: 32 files
- **Untested**: 13 files

### Coverage by Type
- Classes: 85% (34/40)
- Methods: 68% (156/230)
- Lines: 72% (2,340/3,250)
- Branches: 58% (89/153)

### 🔴 Critical Gaps (No Tests)

**1. PaymentProcessor.php** - 0% coverage
- **Risk**: High - handles money
- **Methods untested**: processPayment(), refund(), validate()
- **Recommendation**: Add unit tests immediately

**2. AuthenticationService.php** - 0% coverage
- **Risk**: Critical - security component
- **Methods untested**: authenticate(), validateToken()
- **Recommendation**: Add security tests ASAP

### 🟡 Partial Coverage

**3. UserManager.php** - 45% coverage
- ✅ Tested: getUser(), createUser()
- ❌ Untested: deleteUser(), updatePermissions()
- **Recommendation**: Add tests for delete and permission methods

### ✅ Well Tested

- DataProcessor.php - 95%
- EmailService.php - 88%
- ValidationHelper.php - 100%

### Suggested Actions

1. **Immediate** (Critical):
   - Add tests for PaymentProcessor
   - Add tests for AuthenticationService

2. **This Sprint**:
   - Complete UserManager tests
   - Add integration tests for checkout flow

3. **Next Sprint**:
   - Increase overall coverage to 80%
   - Add E2E tests for critical paths

Detailed Analysis

Method-Level Coverage

## DataProcessor.php Coverage

| Method | Tested? | Coverage | Priority |
|--------|---------|----------|----------|
| processData() | ✅ Yes | 100% | - |
| validateInput() | ✅ Yes | 90% | Low |
| handleError() | ❌ No | 0% | High |
| formatOutput() | ⚠️ Partial | 60% | Medium |

### Untested Code Paths

**handleError() method:**
```php
public function handleError($error) {
  // Line 45: No test coverage
  if ($error instanceof ValidationException) {
    return $this->formatValidationError($error);
  }
  // Line 49: No test coverage
  if ($error instanceof DatabaseException) {
    return $this->formatDatabaseError($error);
  }
  // Line 53: Tested
  return $this->formatGenericError($error);
}

Missing test cases:

• ValidationException handling
• DatabaseException handling
• Edge case: null error

Suggested test:

public function testHandleValidationException(): void {
  $exception = new ValidationException('Invalid input');
  $result = $this->processor->handleError($exception);
  $this->assertStringContains('validation error', $result);
}

## Integration with /test-coverage Command

- **This Skill**: Quick coverage checks
  - "Is this function tested?"
  - "What's missing tests?"
  - Single file/class analysis

- **`/test-coverage` Command**: Comprehensive coverage analysis
  - Full project coverage report
  - Trend analysis over time
  - CI/CD integration
  - Detailed HTML reports

## Coverage Goals

### Industry Standards

- **Minimum**: 70% coverage
- **Good**: 80% coverage
- **Excellent**: 90%+ coverage

**But remember**: 100% coverage ≠ bug-free code

### What to Focus On

**High Priority:**
- Authentication/authorization
- Payment processing
- Data validation
- Security-sensitive code
- Critical business logic

**Medium Priority:**
- API endpoints
- Form handlers
- Data transformations
- Email notifications

**Low Priority:**
- Simple getters/setters
- Configuration classes
- View rendering
- Logging statements

## Quick Commands

### PHP (PHPUnit)

```bash
# Text coverage report
vendor/bin/phpunit --coverage-text

# HTML coverage report
vendor/bin/phpunit --coverage-html coverage/

# Coverage for specific test
vendor/bin/phpunit --coverage-text tests/Unit/DataProcessorTest.php

# Kanopi projects
ddev exec vendor/bin/phpunit --coverage-html coverage/

JavaScript (Jest)

# Terminal coverage
npm test -- --coverage

# HTML report
npm test -- --coverage --coverageReporters=html

# Watch mode with coverage
npm test -- --coverage --watch

# Coverage for specific file
npm test -- --coverage DataProcessor.test.js

Common Gaps & Solutions

Gap 1: Error Handling

Untested:

try {
  $this->processData($data);
} catch (Exception $e) {
  // Untested catch block
  $this->logger->error($e->getMessage());
}

Solution:

public function testProcessDataWithException(): void {
  $this->expectException(ProcessingException::class);
  $this->processor->processData([]);
}

Gap 2: Edge Cases

Untested:

• Empty arrays
• Null values
• Maximum values
• Boundary conditions

Solution: Add tests for each edge case

Gap 3: Integration Points

Untested:

• Database interactions
• API calls
• File system operations

Solution: Add integration tests or use mocks

Coverage Best Practices

1. Test behavior, not coverage - Don't chase 100% blindly
2. Focus on critical paths - Test important code thoroughly
3. Test edge cases - Empty, null, min, max values
4. Test error paths - Exceptions and error handling
5. Keep tests fast - Slow tests won't run
6. Update tests with code - Keep tests current

Resources

• PHPUnit Code Coverage
• Jest Coverage
• Code Coverage Best Practices