public boolean isSuccess() {
    return httpStatus != null && httpStatus >= 200 && httpStatus < 300;
  }
@Test
  public void isSuccess_returns_false_if_failed_to_send_http_request() {
    WebhookDelivery delivery = newBuilderTemplate()
      .setError(new IOException("Fail to connect"))
      .build();

    assertThat(delivery.isSuccess()).isFalse();
  }