You are authoring unit tests.
The unit tests must test code that consumes sealed classes.
You need to create, maintain, and inject dependencies in the unit tests.
Which isolation method should you use?

A.
Shim types

B.
Hard-coded implementation

C.
Stub types

D.
T4 text templates and code generation

Explanation:
http://msdn.microsoft.com/en-us/library/hh549176.aspx
Shim types are one of two technologies that the Microsoft Fakes Framework uses to let you
easily isolate components under test from the environment. Shims divert calls to specific
methods to code that you write as part of your test. Many methods return different results
dependent on external conditions, but a shim is under the control of your test and can return
consistent results at every call. This makes your tests much easier to write.