Well it would have been nice if he stated his interpretation of the Liskov Substitution Principle. The way i understood it best was here [1]. A subclass should

Well it would have been nice if he stated his interpretation of the Liskov Substitution Principle. The way i understood it best was here [1]. A subclass should behave in a way that it never cause problems when it is used instead of the base class. In concrete terms: * No new exceptions are allowed to be thrown, unless they are subtypes of the exception thrown by the base class * Preconditions cannot be strengthend by the subtype * Postconditions cannot be weakened by the subtype For me it is really the focus of using inheritance only if you want substitutability. Otherwise go with composition. === [1] https://youtu.be/8ZJ8BVlDIQ4?t=1762 https://youtu.be/8ZJ8BVlDIQ4?t=1762