How to mock filestream? [closed]

This test method was working in 8.8 but isn't in 9.1.2, not sure what changed - or more specifically  what is the correct way? Here is a sample test - it only fails to verify the close was called on the file stream:

[TestMethod]

        public void TestMethod1()

        {

            FileStream fakeFs = Isolate.Fake.AllInstances<FileStream>();

            Isolate.WhenCalled(() => File.Open("", FileMode.Create)).DoInstead((context) =>

            {

                string path = context.Parameters[0] as string;

                return new FileStream(path, FileMode.Create);

            });

            

            Isolate.WhenCalled(() => fakeFs.Close()).DoInstead((context) =>

            {

                Debug.WriteLine("place holder");

            });

            Isolate.WhenCalled(() => File.Delete("")).IgnoreCall();

            string directoryName = Directory.GetCurrentDirectory();

            string testFile = Path.Combine(directoryName, "Testfile808.txt");

            FileStream fs = File.Open(testFile, FileMode.Create);

            fs.Close();

            File.Delete(testFile);

            Isolate.Verify.WasCalledWithAnyArguments(() => File.Open("", FileMode.Create));              

            Isolate.Verify.WasCalledWithAnyArguments(() => File.Delete(""));

            Isolate.Verify.WasCalledWithAnyArguments(() => fakeFs.Close());

        }