> One major thing I like about having to implement a defined interface is that it forces people creating an API to actually define what that interface is. And i

> One major thing I like about having to implement a defined interface is that it forces people creating an API to actually define what that interface is. And in typing out that interface there's a fair chance they'll actually write doc comments. This has another interesting beneficial side-effect, when embraced: it often leads not just to better API design, but better design in general. Defining an interface necessarily means thinking about it. Which in turn generally leads to thinking about how it’s consumed, at least a fuzzy picture of the code implementing it. All of which can also percolate out into other parts of a system.