...a new feature in next release of .NET -- "Friend Assemblies", that does precisely what you're suggesting. It will use an assembly-level custom attribute called "InternalsVisibleTo", that grants access to a named "friend" assembly (Omer.B in this example) -- for all "internal" types...John Lam describes how friend assemblies will be very useful for implementing unit tests. via [Cook Computing]
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p dir="ltr"> I've always been of the "with friends like these, who needs enemies," school, but unit testing is a compelling counter argument.