@Test
 public void accessControlAllowHeaders() {
   List<String> allowedHeaders = headers.getAccessControlAllowHeaders();
   assertThat(allowedHeaders, Matchers.emptyCollectionOf(String.class));
   headers.setAccessControlAllowHeaders(Arrays.asList("header1", "header2"));
   allowedHeaders = headers.getAccessControlAllowHeaders();
   assertEquals(allowedHeaders, Arrays.asList("header1", "header2"));
 }