case(2016 * 2 * 08 + 0, "AAAAA");
    case(2016 * 2 * 08 + 1, "AAAAA");
    case(2016 * 2 * 09 - 1, "AAAAA");
    case(2016 * 2 * 09 + 0, "AAAA");
    case(2016 * 2 * 09 + 1, "AAAA");
    case(2016 * 2 * 10 - 1, "AAAA");
    case(2016 * 2 * 10 + 0, "AAA");
    case(2016 * 2 * 10 + 1, "AAA");
    case(2016 * 2 * 11 - 1, "AAA");
    case(2016 * 2 * 11 + 0, "AA");
    case(2016 * 2 * 11 + 1, "AA");
    case(2016 * 2 * 12 - 1, "AA");
    case(2016 * 2 * 12 + 0, "A");
    case(2016 * 2 * 12 + 1, "A");
    case(2016 * 2 * 13 - 1, "A");
    case(2016 * 2 * 13 + 0, "A");
    case(2016 * 2 * 13 + 1, "A");
    case(u32::max_value(), "A");
  }

  #[test]
  fn serde() {
    let rune = Rune(0);
    let json = "\"A\"";
    assert_eq!(serde_json::to_string(&rune).unwrap(), json);
    assert_eq!(serde_json::from_str::<Rune>(json).unwrap(), rune);
  }
}