val url =
      HttpUrl
        .Builder()
        .scheme("http")
        .username("a:\u0001@/\\?#%b")
        .password("c:\u0001@/\\?#%d")
        .host("ef")
        .port(8080)
        .addPathSegment("g:\u0001@/\\?#%h")
        .query("i:\u0001@/\\?#%j")
        .fragment("k:\u0001@/\\?#%l")
        .build()
    assertThat(url.toString())
      .isEqualTo(

   * "12AB" is the four hexadecimal digits representing the 16-bit code unit.
   */
  private static String showCharacter(char c) {
    String hex = "0123456789ABCDEF";
    char[] tmp = {'\\', 'u', '\0', '\0', '\0', '\0'};
    for (int i = 0; i < 4; i++) {
      tmp[5 - i] = hex.charAt(c & 0xF);
      c = (char) (c >> 4);
    }
    return String.copyValueOf(tmp);
  }

  // Fast matchers