Ah, I think I know what's going on. In your case, you should use
to prevent the cctor from executing. When you use Isolate.WhenCalled, you can specify any method you want, fake or "live", and its behavior will be overwritten, you don't need to explicitly call Fake.StaticMethod().
Also, you can use the Isolator API to verify the argument like this:
string info = "foo";
Isolate.WhenCalled(() => IAmAStaticClass.GetInfo(info))
By using WithExactArguments you instruct Isolator to check the argument values. They are ignored by default.
Hope that helps.