Can it be done without using TypeMock Islolator? I've found a few suggestions online such as passing in a metadata only connection string, however nothing I've come across besides TypeMock seems to truly allow for a mock ObjectContext that can be injected into services for unit testing. Do I plunk down the $$ for TypeMock, or are there alternatives? Has nobody managed to create anything comparable to TypeMock that is open source?
I'm unit testing EF4 easily without mocking. What I did was create a repository interface using the code from http://elegantcode.com/2009/12/15/entity-framework-ef4-generic-repository-and-unit-of-work-prototype/ as a basis I then created an InMemoryRepository<T> class that used the IRepository interface. I then replaced the IObjectSet<T> with a List<T> inside of the class and changed the retrieval methods accordingly.
Thus if you need to do unit testing, pass in the InMemoryRepository rather than the DataRepository.
Put your Linq2Entity query behind an interface, unit test it in isolation against a real database.
Write tests for your business logic with mocks for your query interfaces. Don't let Linq bleed into your business logic!
Don't use the RepositoryPattern!
Wrap the ObjectContext in a proxy class. Then inject that into your classes.
I don't think the repository pattern is the only answer to the question (it avoids the problem, sure)
I liked this answer - I think more appropriate for introducing tests to an existing codebase Creating Interface for ObjectContext
来源：https://stackoverflow.com/questions/2703100/ef4-possible-to-mock-objectcontext-for-unit-testing