Converter<String, String> nullsAreHandled = sillyConverter(true);
    assertThat(nullsAreHandled.convert("foo")).isEqualTo("forward");
    assertThat(nullsAreHandled.convert(null)).isNull();
    assertThat(nullsAreHandled.reverse().convert("foo")).isEqualTo("backward");
    assertThat(nullsAreHandled.reverse().convert(null)).isNull();
  }

  private static Converter<String, String> sillyConverter(boolean handleNullAutomatically) {