@Test
public void builder() throws Exception {

  assertThat(requestKey.getMethod(), equalTo(HttpMethod.GET));
  assertThat(requestKey.getUrl(), equalTo("a"));
  assertThat(requestKey.getHeaders().size(), is(1));
  assertThat(requestKey.getHeaders().fetch("my-header"),
      equalTo((Collection<String>) Arrays.asList("val")));
  assertThat(requestKey.getCharset(), equalTo(StandardCharsets.UTF_16));
}