I am investigating the ADO.NET Entity Framework in combination with unit testing. A recommended way is described by Scott Allan:
Testability and Entity Framework 4.0
The article involves the code generation with POCOS.
My first impression: The manual effort to introduce and maintain this architecture is high. Before a deep dive I am interested in any real world experience.
Using POCO objects makes unit testing easier, but doesn’t help you in making the code that uses LINQ queries over those POCO objects testable. Take a look at this article. It describes how to hide EF behind an abstraction, while still allowing to use LINQ queries over it.