}
        };
    assertThrows(IllegalStateException.class, iter::hasNext);
  }

  // Technically we should test other reentrant scenarios (9 combinations of
  // hasNext/next/peek), but we'll cop out for now, knowing that peek() and
  // next() both start by invoking hasNext() anyway.

  private static final ImmutableSet<String> VALID_NAME =
      ImmutableSet.of(
          // keep-sorted start
          "123.cn",
          "8server.shop",
          "a" + DELTA + "b.com",
          "abc.a23",
          "biz.com.ua",
          "f--1.com",
          "f--o",
          "f-_-o.cOM",
          "f11-1.com",
          "fOo",
          "f_a",