The Complexity of Writing Code

I like to tell people that laws are like Magic the Gathering. Every individual rule makes sense when you look at it on one card, but when it comes into conflict with other cards,. There's no way to guarantee exactly how people are going to interpret them. When you have multiple systems interacting together, you're not sure whether stuff that is a unit tested, perfect, exemplary system is going to work in the real world against another one. And that's why I like integration tests.