/// <summary>

    /// Save the FileUpload data as a temp file

    /// </summary>

    /// <param name="sender"></param>

    /// <param name="fileUpload"></param>

    /// <returns></returns>

    public string SaveFileUploadAsTempFile(FileUpload fileUpload)

    {

        // Generate a Temp file in the App_Data\Temp folder

        // and return the file name

        string tempFile = GetTempFile();

        // Store the FileUpload control's InputStream (the file)

        // to a fileData stream.  We do it this way for Unit Testing

        // purposes

        Stream fileData = fileUpload.PostedFile.InputStream;

        // Use the Stream's StrToFile extension to save the contents

        // to our temp file

        fileData.StrToFile(tempFile);

        // Return the name of the temp file that holds our

        // file contents

        return tempFile;

    }

using System;

using System.IO;

using System.Web;

using System.Web.UI.WebControls;

using System.Text;

using System.Linq;

using System.Collections.Generic;

using Microsoft.VisualStudio.TestTools.UnitTesting;

using TypeMock;

using HttpUtility.Tests.Base;

using HttpUtility.Storage;

// Holds our string and stream extensions for StrToFile()

using Library.Utility.Extensions;

namespace HttpUtility.Tests

{

    /// <summary>

    /// Summary description for FileUploadFixture

    /// </summary>

    [TestClass]

    public class FileUploadFixture : TestBase

    {

        public FileUploadFixture() {}

        [TestMethod]

        public void FileUpload_ControlCanWriteToAppData()

        {

            // The TestBase:HttpContextBase constructor will

            // create a HttpContext.Current if it is null  BLOGGED HERE

            HttpContext MockContext = HttpContext.Current;

            // Assert that we have a MockContext

            Assert.IsNotNull(MockContext, 

                "HttpContextBase should create HttpContext");

            // When the context is retrieved the PhysicalPath

            // property of our TestBase class will be set

            Assert.IsNotNull(PhysicalPath);

            // Dynamically generate our MockFolderPath using the 

            // TestBase:HttpContextBase.PhysicalPath property 

            MockFolderPath = PhysicalPath.Replace("default.aspx", "App_Data");

            // Instantiate our file Utility class

            FileUploadUtil fileUploadUtil = new FileUploadUtil();

            // Setup the TypeMock recorder

            // When MapPath("App_Data") is requested, supply our 

            // MockFolderPath (public static string in TestBase)

            using (RecordExpectations recorder = RecorderManager.StartRecording())

            {

                // GetTempFile() will request this - we'll return

                // our MockFolderPath when it does

                HttpContext.Current.Server.MapPath("App_Data");

                recorder.Return(MockFolderPath);

            }

            // Use the fileUploadUtil to get Temp file in App_Data\Temp

            string app_dataPath = fileUploadUtil.GetTempFile();

            // Write mockData to temp file using our string extension

            mockData.StrToFile(app_dataPath);

            // Ensure our mockData file exists so we can 

            // pull it into a MockStream

            Assert.IsTrue(File.Exists(app_dataPath));

            // Read temp file containing mockData into file stream

            FileInfo fileInfo = new FileInfo(app_dataPath);

            FileStream MockStream = fileInfo.OpenRead();

            // Instantiate our mock FileUpload control

            FileUpload MockFileUploadControl = new FileUpload();

            // Setup the TypeMock recorder 

            using (RecordExpectations recorder = RecorderManager.StartRecording())

            {

                // GetTempFile() will request this - we'll return

                // our MockFolderPath when it does

                HttpContext.Current.Server.MapPath("App_Data");

                recorder.Return(MockFolderPath);

                // When the contents from the PostedFile.InputStream is 

                // requested we'll return our MockStream (set above to

                // the contents of app_dataPath)

                recorder.ExpectAndReturn(

                    MockFileUploadControl.PostedFile.InputStream, 

                    MockStream);

            }

            // Call our FileUploadUtil method that will save the 

            // FileUpload control's contents to a temporary file

            string savedFile = fileUploadUtil

                .SaveFileUploadAsTempFile(MockFileUploadControl);

            // Retrieve the file just saved

            string savedXML = savedFile.FileToStr();

            // Assert that it is equal to the data that was in our

            // MockStream

            Assert.AreEqual(mockData, savedXML);

            MockManager.Verify();

        }

        private TestContext testContextInstance;

        /// <summary>

        ///Gets or sets the test context which provides

        ///information about and functionality for the current test run.

        ///</summary>

        public TestContext TestContext

        {

            get

            {

                return testContextInstance;

            }

            set

            {

                testContextInstance = value;

            }

        }

    }

}

Source code available HERE Change Set: 40565