David .Net

    public class Utility
    {
        public static void CreateHttpContext(string absolutePath, string physicalPath, string host, string page, string queryString)
        {
            TextWriter tw = new StringWriter();                    
            HttpWorkerRequest wr = new MyWorkerRequest
            (absolutePath, physicalPath, page, queryString, tw, host);
            HttpContext.Current = new HttpContext(wr);
        }

        public class MyWorkerRequest : SimpleWorkerRequest
        {
            private string localAdd = string.Empty;

            public MyWorkerRequest(string absolutePath, string physicalPath, string page, string query, TextWriter output, string address)
                : base(absolutePath, physicalPath, page, query, output)
            {
                this.localAdd = address;
            }

            public override string GetLocalAddress()
            {
                return this.localAdd;
            }

            public override string MapPath(string virtualPath)
            {
                return Path.Combine(this.GetAppPath(), virtualPath);
            }
        }
    }

/// <summary>
        ///A test for GetServerName
        ///</summary>
        [TestMethod()]
        [DeploymentItem("Test.dll")]
        public void GetServerNameTest()
        {
            Utility.CreateHttpContext("/", @"C:\inetpub\wwwroot\DemoSite", "test.com.tw", "default.aspx", "");

            string expected = "test.com.tw";
            string actual;
            actual = Test_Accessor.GetServerName();
            Assert.AreEqual(expected, actual);
        }