public static <T> Result<T> of() {
    return new Result<>(null);
  }
@Test
  public void test_toString() {
    String errorMessage = "the error";
    Result.Message txtMsg = Result.Message.of(errorMessage);
    assertThat(txtMsg.toString()).contains(errorMessage);
    assertThat(txtMsg.toString()).isNotEqualTo(errorMessage);

    Result.Message msg = Result.Message.ofL10n("issue.error.123", "10");
    assertThat(msg.toString()).contains("issue.error.123").contains("10");
    assertThat(msg.toString()).isNotEqualTo("issue.error.123");
  }