@Override
    public BitMask set(int index) {
        if (index >= 64) {
            return BitMask.getEmpty(index+1).setAll(this).set(index);
        }
        this.mask = this.mask | (1L << index);
        return this;
    }
@Test
  public void testSet() {
      assertThat(new LongBitMask().set(0).toString()).isEqualTo("1");
      assertThat(new LongBitMask().set(1).toString()).isEqualTo("2");
      assertThat(new LongBitMask().set(65).toString()).isEqualTo("0, 2");
  }