public static PrimitiveIterator.OfInt all(int pageCount) {
    return new IndexIterator(0, pageCount, i -> true, i -> i);
  }
@Test
  public void testAll() {
    assertEquals(IndexIterator.all(10), 0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
  }