static String getETag(String output) {
    return "W/" + hash(output.getBytes(UTF_8));
  }
@Test
  public void getETag_should_return_same_value_for_same_input() {
    String input = randomAlphanumeric(200);
    assertThat(ETagUtils.getETag(input)).isEqualTo(ETagUtils.getETag(input));
  }