Interesting Talk: "OO Design for Testability"

I've just watched this interesting talk by Miško Hevery:

• OO Design for Testability

According to Miško Hevery the biggest enemies of testability are:

1. Location of the new Operators. 
2. Work in constructors. 
3. Global State. 
4. Law of Demeter violations.

In this talk he explains why and shows ways to avoid them.