testing-standards

Testing Standards

Guidelines for writing effective tests that catch bugs, enable refactoring, and document behavior.

Testing Pyramid

Prefer more tests at the bottom, fewer at the top:

        /  E2E  \        Few, slow, high confidence
       /----------\
      / Integration \    Some, medium speed
     /----------------\
    /    Unit Tests    \  Many, fast, focused

What to Test

Always Test

• Business logic and calculations
• Edge cases and boundary conditions
• Error handling paths
• Public API contracts
• Security-sensitive code
• Complex conditionals

Usually Skip

• Simple getters/setters
• Framework code (React renders, Express routing)
• Third-party library internals
• Private implementation details
• Logging statements

Unit Tests

Structure: Arrange-Act-Assert

test('calculates total with discount', () => {
  // Arrange
  const cart = new Cart([{ price: 100 }, { price: 50 }]);
  const discount = 0.1;

  // Act
  const total = cart.calculateTotal(discount);

  // Assert
  expect(total).toBe(135);
});

Naming Convention

test('[unit] [action] [expected result] [condition]')

Examples:

• test('User.validate rejects empty email')
• test('calculateTax returns 0 for tax-exempt items')
• test('login redirects to dashboard on success')

Keep Tests Focused

// Bad: Testing multiple behaviors
test('user registration', () => {
  expect(validate(user)).toBe(true);
  expect(hash(password)).toMatch(/^\$2b\$/);
  expect(sendEmail).toHaveBeenCalled();
  expect(db.save).toHaveBeenCalled();
});

// Good: One behavior per test
test('validates user email format', () => { ... });
test('hashes password with bcrypt', () => { ... });
test('sends welcome email after registration', () => { ... });
test('persists user to database', () => { ... });

Integration Tests

Test how components work together:

describe('User Registration Flow', () => {
  test('creates user and sends welcome email', async () => {
    const response = await request(app)
      .post('/api/users')
      .send({ email: '[email protected]', password: 'secure123' });

    expect(response.status).toBe(201);
    expect(await User.findByEmail('[email protected]')).toBeTruthy();
    expect(emailService.sent).toContainEqual(
      expect.objectContaining({ to: '[email protected]' })
    );
  });
});