public void TestFindPreambleHeaderBlockNotFirstShouldThrow()
 {
     using (MemoryStream testStream = new MemoryStream())
     {
         AxCrypt1Guid.Write(testStream);
         VersionHeaderBlock versionHeaderBlock = new VersionHeaderBlock();
         versionHeaderBlock.Write(testStream);
         PreambleHeaderBlock preambleHeaderBlock = new PreambleHeaderBlock();
         preambleHeaderBlock.Write(testStream);
         testStream.Position = 0;
         using (AxCryptReader axCryptReader = AxCryptReader.Create(testStream))
         {
             Assert.That(axCryptReader.Read(), Is.True, "We should be able to read the Guid");
             Assert.That(axCryptReader.CurrentItemType, Is.EqualTo(AxCryptItemType.MagicGuid), "We're expecting to have found a MagicGuid");
             Assert.Throws<FileFormatException>(() => axCryptReader.Read());
         }
     }
 }