public void Shall_clone_header()
        {
            AcceptEncodingHeader original = AcceptEncodingHeader.Parse("gzip");
            AcceptEncodingHeader cloned   = original.DeepClone();

            original.Element = "deflate";
            original.Parameters.Add(new GenericParameter("foo", "bar"));

            Assert.That(cloned.ToString(), Is.EqualTo("gzip"));
            Assert.That(original.ToString(), Is.EqualTo("deflate;foo=bar"));
        }