@Test
 public void modifyRequestHeaders() {
   OperationRequest request =
       this.requestFactory.create(
           URI.create("http://localhost"),
           HttpMethod.GET,
           new byte[0],
           getHttpHeaders(),
           new Parameters(),
           Collections.<OperationRequestPart>emptyList());
   OperationRequest preprocessed = this.preprocessor.preprocess(request);
   assertThat(preprocessed.getHeaders().size(), is(equalTo(2)));
   assertThat(preprocessed.getHeaders(), hasEntry("a", Arrays.asList("alpha")));
   assertThat(preprocessed.getHeaders(), hasEntry("Host", Arrays.asList("localhost")));
 }