@Test
 public void contentType() {
   MediaType contentType = new MediaType("text", "html", Charset.forName("UTF-8"));
   headers.setContentType(contentType);
   assertEquals("Invalid Content-Type header", contentType, headers.getContentType());
   assertEquals(
       "Invalid Content-Type header", "text/html;charset=UTF-8", headers.getFirst("Content-Type"));
 }