test-coverage

On-demand test coverage analysis. Use when identifying untested code, finding test gaps, measuring coverage metrics, or improving test quality. Trigger keywords - "test coverage", "coverage report", "untested code", "test gaps", "missing tests", "coverage metrics".

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Repository: MadAppGang/claude-code
Last source activity: January 28, 2026 at 12:28
Detected SKILL.md language: English
Stars: 278
Forks: 29

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function divide(a: number, b: number): number {
  if (b === 0) {              // Line 1: COVERED
    throw new Error('Div 0'); // Line 2: NOT COVERED
  }
  return a / b;               // Line 3: COVERED
}

// Test only covers normal case
test('divides numbers', () => {
  expect(divide(10, 2)).toBe(5);
});

// Line Coverage: 66% (2/3 lines)

function getUserStatus(user: User): string {
  if (user.isActive) {     // Branch 1: true (COVERED)
    if (user.isPremium) {  // Branch 2: true (NOT COVERED)
      return 'premium';    // NOT COVERED
    }
    return 'active';       // COVERED
  }
  return 'inactive';       // Branch 1: false (NOT COVERED)
}

// Test only covers active non-premium
test('returns status', () => {
  expect(getUserStatus({ isActive: true, isPremium: false })).toBe('active');
});

// Branch Coverage: 33% (1/3 branches)
// Line Coverage: 60% (3/5 lines)

// auth.ts
export function login(user: string, pass: string) { ... }    // COVERED
export function logout() { ... }                             // COVERED
export function resetPassword(email: string) { ... }         // NOT COVERED
export function changePassword(old: string, new: string) { ... } // NOT COVERED

// Function Coverage: 50% (2/4 functions)

// Single line, multiple statements
const x = 1, y = 2, z = 3;

// Line coverage: 1 line
// Statement coverage: 3 statements

# Test Coverage Gap Analysis

**Generated**: 2026-01-28 14:32:00
**Coverage**: 68% (Target: 80%)
**Files Analyzed**: 247
**Critical Gaps**: 12 files

## Executive Summary

**Overall Coverage**:
- Line Coverage: 68% (Target: 80%) - 12% below
- Branch Coverage: 54% (Target: 75%) - 21% below
- Function Coverage: 71% (Target: 85%) - 14% below

**Risk Assessment**: MEDIUM-HIGH
- 12 critical files under 50% coverage
- 23 high-priority functions untested
- 47 error handling branches untested

## Critical Gaps (Priority 1)

### [GAP-001] Authentication Module
**File**: src/auth/AuthService.ts
**Line Coverage**: 34% (Target: 95%+)
**Branch Coverage**: 22%
**Risk**: CRITICAL

**Untested Code Paths**:
```typescript
// CRITICAL: No tests for password reset flow
async resetPassword(email: string): Promise<void> {
  const user = await this.userRepo.findByEmail(email);
  if (!user) {
    throw new NotFoundError('User not found'); // UNTESTED
  }
  const token = generateResetToken();           // UNTESTED
  await this.emailService.sendResetEmail(       // UNTESTED
    user.email,
    token
  );
}

// CRITICAL: No tests for token expiry
validateResetToken(token: string): boolean {
  const decoded = jwt.verify(token, SECRET);
  if (Date.now() > decoded.exp) {              // UNTESTED
    return false;
  }
  return true;
}

async processPayment(order: Order): Promise<PaymentResult> {
  try {
    const charge = await stripe.charges.create({ // TESTED
      amount: order.total,
      currency: 'usd',
      source: order.paymentToken
    });

    if (charge.status === 'failed') {            // UNTESTED
      await this.handleFailedPayment(order);     // UNTESTED
      throw new PaymentError('Payment failed');
    }

    await this.fulfillOrder(order);              // TESTED
    return { success: true, chargeId: charge.id };
  } catch (error) {
    if (error.code === 'card_declined') {        // UNTESTED
      await this.notifyCardDeclined(order);      // UNTESTED
    }
    throw error;                                 // UNTESTED
  }
}

validateUserData(data: UserInput): ValidationResult {
  const errors: string[] = [];

  if (!data.email || !data.email.includes('@')) {  // Partially tested
    errors.push('Invalid email');
  }

  if (data.password.length < 8) {                  // UNTESTED
    errors.push('Password too short');
  }

  if (!/[A-Z]/.test(data.password)) {              // UNTESTED
    errors.push('Password needs uppercase');
  }

  if (!/[0-9]/.test(data.password)) {              // UNTESTED
    errors.push('Password needs number');
  }

  return { valid: errors.length === 0, errors };
}

async getUser(req: Request, res: Response) {
  try {
    const user = await this.userService.getById(req.params.id);
    res.json(user);                                 // TESTED
  } catch (error) {
    if (error instanceof NotFoundError) {           // UNTESTED
      res.status(404).json({ error: 'Not found' });
    } else if (error instanceof ValidationError) {  // UNTESTED
      res.status(400).json({ error: error.message });
    } else {
      res.status(500).json({ error: 'Server error' }); // UNTESTED
    }
  }
}

Module Coverage Breakdown:

├── src/auth/               34% (CRITICAL - needs work)
├── src/payments/           41% (CRITICAL - needs work)
├── src/users/              62% (below target)
├── src/api/handlers/       59% (below target)
├── src/services/           72% (above target ✓)
├── src/utils/              84% (good ✓)
├── src/database/           91% (excellent ✓)
└── src/components/         77% (good ✓)

Overall: 68%
Target: 80%
Gap: -12%

// BAD: No assertion
test('creates user', async () => {
  await createUser({ name: 'John' });
});

// GOOD: Verify behavior
test('creates user', async () => {
  const user = await createUser({ name: 'John' });
  expect(user.id).toBeDefined();
  expect(user.name).toBe('John');
});

// BAD: Always passes
test('validates email', () => {
  const result = validateEmail('test@example.com');
  expect(result).toBeTruthy(); // Any truthy value passes
});

// GOOD: Specific assertion
test('validates email', () => {
  expect(validateEmail('test@example.com')).toBe(true);
  expect(validateEmail('invalid')).toBe(false);
});

// BAD: Mocks everything, tests nothing
jest.mock('../UserService');

// GOOD: Mock only external dependencies
jest.mock('../EmailService');
// UserService tested with real implementation

// BAD: Depends on timing
test('debounces input', async () => {
  fireEvent.change(input, { target: { value: 'test' } });
  await new Promise(resolve => setTimeout(resolve, 100)); // Flaky!
  expect(mockFn).toHaveBeenCalledTimes(1);
});

// GOOD: Use fake timers
test('debounces input', () => {
  jest.useFakeTimers();
  fireEvent.change(input, { target: { value: 'test' } });
  jest.advanceTimersByTime(300);
  expect(mockFn).toHaveBeenCalledTimes(1);
});


## Coverage Report Format

### Standard Coverage Output

**Jest/Vitest**:

File	% Stmts	% Branch	% Funcs	% Lines	Uncovered Line #s
All files	68.23	54.12	71.45	68.23
auth/	34.56	22.31	41.23	34.56
AuthService	34.56	22.31	41.23	34.56	42-67,89-102
payments/	41.23	29.45	50.00	41.23
PaymentSvc	41.23	29.45	50.00	41.23	23-34,56-78
users/	62.34	48.12	65.23	62.34
UserService	62.34	48.12	65.23	62.34	112-123,145
----------------	---------	----------	---------	---------	-------------------


**Go**:


**Rust (tarpaulin)**:


## Integration with Dev Plugin

### With Test Architect Agent

Request comprehensive test creation:


The test-architect agent will:
1. Identify gaps using this skill
2. Generate test files
3. Run tests and verify coverage improvement

### With Audit Skill

Combine coverage with security:


### With Optimize Skill

Balance coverage with performance:


## Best Practices

### 1. Set Coverage Targets by Risk

**Critical Code** (95%+ coverage):
- Authentication and authorization
- Payment processing
- Data validation
- Security checks

**Business Logic** (80%+ coverage):
- Core features
- API endpoints
- State management

**Utilities** (70%+ coverage):
- Helper functions
- Formatters
- Parsers

**Infrastructure** (50%+ coverage):
- Configuration
- Build scripts
- Tooling

### 2. Focus on Untested Branches

Branch coverage > line coverage for finding bugs.

**Example**:
```typescript
// 100% line coverage, 50% branch coverage
function process(data: Data | null) {
  const result = data ? data.value : 0; // Both branches needed
  return result * 2;
}

// Test only null case - 100% lines, 50% branches
test('handles null', () => {
  expect(process(null)).toBe(0);
});

// Need both cases
test('handles data', () => {
  expect(process({ value: 5 })).toBe(10);
});

test('calls getUserById', () => {
  const spy = jest.spyOn(service, 'getUserById');
  component.loadUser(123);
  expect(spy).toHaveBeenCalledWith(123);
});

test('displays user name after loading', async () => {
  render(<UserProfile userId={123} />);
  await waitFor(() => {
    expect(screen.getByText('John Doe')).toBeInTheDocument();
  });
});

# .github/workflows/test.yml
- name: Run tests with coverage
  run: npm test -- --coverage

- name: Check coverage threshold
  run: |
    COVERAGE=$(jq '.total.lines.pct' coverage/coverage-summary.json)
    if (( $(echo "$COVERAGE < 80" | bc -l) )); then
      echo "Coverage $COVERAGE% below 80%"
      exit 1
    fi

#!/bin/bash
# Run tests on changed files
CHANGED_FILES=$(git diff --cached --name-only --diff-filter=ACM | grep '\.ts$')
if [ -n "$CHANGED_FILES" ]; then
  npm test -- --findRelatedTests $CHANGED_FILES --coverage
fi

I just added user profile editing. Check test coverage for this feature.

User Profile Feature Coverage: 58%

Files:
- UserProfile.tsx: 72% (needs: error handling tests)
- useUserProfile.ts: 45% (needs: loading state, error state)
- updateUser.ts: 67% (needs: validation error cases)

Critical Gaps:
- No test for update failure
- No test for network error
- No test for validation errors

Recommended Tests: 8
Estimated Coverage After: 89%

Check if we meet 80% coverage threshold for deployment

Current Coverage: 76% (Target: 80%)
Status: BLOCKED

Modules Below Target:
- auth/: 34% (need +46%)
- payments/: 41% (need +39%)
- api/handlers/: 59% (need +21%)

Quickest Path to 80%:
1. Add auth error handling tests (+8%)
2. Add payment failure tests (+6%)
3. Add API validation tests (+4%)

Estimated Effort: 2 days

We're refactoring the auth module. What's our test coverage there?

Auth Module Coverage: 34%

Risk Assessment: HIGH
- 66% of code is untested
- No tests for password reset
- No tests for session expiry
- Limited tests for error cases

Recommendation: STOP
Before refactoring:
1. Increase coverage to 80%+ (add 23 tests)
2. Add integration tests for auth flow
3. Document expected behavior

Refactoring without tests = high regression risk

npm test -- --coverage --collectCoverageFrom='src/**/*.{ts,tsx}'

go test -coverprofile=coverage.out ./...
go tool cover -html=coverage.out

cargo tarpaulin --out Html --output-dir coverage

name	test-coverage
description	On-demand test coverage analysis. Use when identifying untested code, finding test gaps, measuring coverage metrics, or improving test quality. Trigger keywords - "test coverage", "coverage report", "untested code", "test gaps", "missing tests", "coverage metrics".
version	0.1.0
tags	["dev","testing","coverage","quality","gaps"]
keywords	["test-coverage","coverage","gaps","untested","metrics","testing","quality"]
plugin	dev
updated	"2026-01-28T00:00:00.000Z"

name	test-coverage
description	On-demand test coverage analysis. Use when identifying untested code, finding test gaps, measuring coverage metrics, or improving test quality. Trigger keywords - "test coverage", "coverage report", "untested code", "test gaps", "missing tests", "coverage metrics".
version	0.1.0
tags	["dev","testing","coverage","quality","gaps"]
keywords	["test-coverage","coverage","gaps","untested","metrics","testing","quality"]
plugin	dev
updated	"2026-01-28T00:00:00.000Z"

File	Coverage	Untested Lines	Priority
src/utils/DateFormatter.ts	67%	12	MEDIUM
src/services/EmailService.ts	65%	23	MEDIUM
src/middleware/RateLimiter.ts	63%	18	MEDIUM
src/database/Migrations.ts	58%	34	LOW

test-coverage

Source facts

Install options

Review the source files

More from this repository

Test Coverage Skill

Overview

More from this repository

Test Coverage Skill

Overview

Coverage Metrics

1. Line Coverage

2. Branch Coverage

3. Function Coverage

4. Statement Coverage

Gap Analysis

Identifying Untested Code

Gap Report Format

[GAP-002] Payment Processing

High Priority Gaps (Priority 2)

[GAP-003] User Registration Validation

[GAP-004] API Error Handling

Medium Priority Gaps

Files Under 70% Coverage

Coverage by Module

Untested Critical Scenarios

Recommendations

Immediate Actions (This Week)

Short Term (This Month)

Long Term (This Quarter)

Test Quality Assessment

Test Smells Detected

3. Test Behavior, Not Implementation

4. Use Coverage to Find Gaps, Not as Goal

5. Automate Coverage Checks

Examples

Example 1: New Feature Coverage Check

Example 2: Pre-Deployment Coverage Gate

Example 3: Identify Regression Risk

Stack-Specific Patterns

React/TypeScript (Jest + RTL)

Go

Rust

Conclusion