assertTrue(actual.contains(list(1, 4)));
    assertTrue(actual.contains(list(2, 3)));
    assertTrue(actual.contains(list(2, 4)));
    assertFalse(actual.contains(list(3, 1)));
  }

  public void testCartesianProduct_indexOf() {
    List<List<Integer>> actual = cartesianProduct(list(1, 2), list(3, 4));
    assertEquals(0, actual.indexOf(list(1, 3)));
    assertEquals(1, actual.indexOf(list(1, 4)));