assertEquals(-1, actual.indexOf(list(3, 1)));

    assertEquals(-1, actual.indexOf(list(1)));
    assertEquals(-1, actual.indexOf(list(1, 1, 1)));
  }

  public void testCartesianProduct_lastIndexOf() {
    List<List<Integer>> actual = cartesianProduct(list(1, 1), list(2, 3));
    assertThat(actual.lastIndexOf(list(1, 2))).isEqualTo(2);
    assertThat(actual.lastIndexOf(list(1, 3))).isEqualTo(3);