input = Arrays.copyOf(input, input.length);
    UnsignedLongs.sort(input, from, to);
    assertThat(input).isEqualTo(expected);
  }

  public void testSortIndexed() {
    testSort(new long[] {}, 0, 0, new long[] {});
    testSort(new long[] {2}, 0, 1, new long[] {2});
    testSort(new long[] {2, 1, 0}, 0, 2, new long[] {1, 2, 0});