public void AppendText() { string tempFile = Path.GetTempFileName(); string expected = "This is a test."; ExtendedFileInfo efi = new ExtendedFileInfo(tempFile); Assert.IsNotNull(efi); using (StreamWriter writer = efi.AppendText()) { Assert.IsNotNull(writer); writer.Write(expected); } string actual = File.ReadAllText(tempFile); Assert.AreEqual(expected, actual); }