The Rectangle-Square Problem: What It Teaches Us About Liskov Substitution Principle (LSP)
TL;DR LSP means you can use subtype objects anywhere you use base type objects without breaking code. Square/Rectangle inheritance that breaks existing code? That’s a classic LSP problem. Watch for subclasses that throw unexpected exceptions or silently change behavior. When behaviors are too different, reach for composition instead of inheritance. Make interfaces that clearly show what objects can and can’t do to avoid surprises. LSP violations often sneak past unit tests and show up as runtime bugs. The Liskov Substitution Principle isn’t just academic theory - it helps you avoid those “it worked yesterday” bugs that show up in production. When a subclass doesn’t behave like its parent promises, your code breaks in ways that unit tests often miss. ...