public List<Exception> errors() {
    return Collections.unmodifiableList(this.errors);
  }
@Test
  void errors() {
    final var e = new BusinessException("unhandled");
    final var retry = new Retry<String>(
        () -> {
          throw e;
        },
        2,
        0
    );
    try {
      retry.perform();
    } catch (BusinessException ex) {
      //ignore
    }

    assertThat(retry.errors(), hasItem(e));
  }