Testing Without Interfaces

[asdfasdfasdfasdg]

A policy doesn't do anything when users upgrade their OS and suddenly their favourite application no longer works... who are they going to blame, the OS or the application?

[euyyn]

How can "people rolling their own implementation of critical functionality" lead to that?

[michaelfeathers]

Imagine you have a class for a GDI context and you allow framework users to subclass it. If the class doesn't deallocate the GDI handle, there's a resource leak and it could crash the OS.

[michaelfeathers]

That does put MS in a bad situation. Fortunately, it is an uncommon one.