assertEquals(emptyList(), fromList);
  }

  @SafeVarargs
  private static <E> List<E> list(E... elements) {
    return ImmutableList.copyOf(elements);
  }

  public void testCartesianProduct_binary1x1() {
    assertThat(cartesianProduct(list(1), list(2))).contains(list(1, 2));
  }

  public void testCartesianProduct_binary1x2() {
    assertThat(cartesianProduct(list(1), list(2, 3)))

  }

  private static void assertEmpty(Set<? extends List<?>> set) {
    assertTrue(set.isEmpty());
    assertEquals(0, set.size());
    assertFalse(set.iterator().hasNext());
  }

  public void testCartesianProduct_binary1x1() {
    assertThat(cartesianProduct(set(1), set(2))).contains(list(1, 2));
  }

  public void testCartesianProduct_binary1x2() {
    assertThat(cartesianProduct(set(1), set(2, 3)))