Square and rectangle

The classic example of a problem that violates the Liskov Substitution Principle is the Circle-Ellipse problem, sometimes called the Square-Rectangle problem.

By all means, it seems like you should be able to define a class Rectangle, with attributes h and w (for height and width), and then define a class Square that inherits from the Rectangle. After all, a square "is-a" rectangle!

Unfortunately, this intuition doesn't apply to object-oriented design.