Good interfaces should primarily have reasonable and well documented pre and post conditions. This is very apparently not so in the oil change example in the article.
It's completely stunning to me how frequently this is forgotten in spite of having been a key component of object oriented programming when it was invented (ie smalltalk days, before I was born).
It's completely stunning to me how frequently this is forgotten in spite of having been a key component of object oriented programming when it was invented (ie smalltalk days, before I was born).