protected <G> G doGet(String token, HttpUrl url, Function<String, G> handler) {
    Request request = prepareRequestWithBearerToken(token, GET, url, null);
    return doCall(request, handler);
  }
@Test
  public void validate_handler_call_on_empty_body() {
    server.enqueue(new MockResponse().setResponseCode(200)
            .setBody(""));
    assertThat(underTest.doGet("token", server.url("/"),  Function.identity()))
            .isEmpty();
  }