Non si finisce mai di scoprire cose nuove... VB2005 non
supporta InternalsVisibleTo... uff... meglio che l'ho scoperto adesso piuttosto che
durante un progetto... 
I’ve gotten some feedback from Visual Basic .NET developers having
trouble following my “How To” on code
coverage and IL Merge. I turns out that the Visual Basic .NET 2005 compiler
doesn’t support the InternalsVisibleTo
attribute. After adding the attribute to an assembly, you won’t get any
IntelliSense for the internal, or fiend in Visual Basic lingo, members. When
you try to build the solution the compiler will raise a BC30390 compilation
error...
Fonte: Visual Basic 2005 Does Not Support Friend Assemblies