File is a framework [mscrolib] class and it can't be mocked as like other static methods. You don’t need to do Mock.SetupStatic(Of System.IO.File)(Behavior.Strict) for File. Therefore, you can directly jump into to the arrrange part [paritial mocking of members]. Also, you need to provide a MockClass attribute on top of your test class.
Finally, you can take a look at the MsCorlibFixture in the Elevated tests in C# examples. You will find examples of mocking File.
Addtionally, there was an issue with static methods for non framework methods. If you need a build urgently, I can personally send you one. All you have to do is to send a drop location in the previously mentioned email in this thread.
Hope that helps,
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