👨‍💼 Perfect! You've demonstrated dependency injection in action.

🦉 Notice how EmailService doesn't need to know about MockLogger or SilentLogger. It just accepts any Logger (or subclass). This is the power of composition:

💰 Dependency injection is a key benefit of composition. By accepting dependencies through the constructor (or methods), you make your code more flexible and testable. This is why composition is often preferred over inheritance—it gives you more control and flexibility.