Liskov Substitution
Domain: Design Principles
🎯 Motivation
Subtypes must be replaceable for their base types without breaking the program. If a subclass changes behavior unexpectedly, code that relies on the parent class will fail in confusing ways.
📋 Concrete Example
If Bird has a fly() method, then Penguin should not inherit Bird directly. A penguin that throws an error on fly() violates substitution, so restructure the hierarchy.
🔗 Analogy
If you order a “vehicle” and receive a bicycle, you can still ride it to school. But if you receive a toy car that cannot move, the promise is broken — substitution failed.