}

  public void testCartesianProduct_binary0x0() {
    Set<Integer> mt = emptySet();
    assertEmpty(cartesianProduct(mt, mt));
  }

  public void testCartesianProduct_binary0x1() {
    Set<Integer> mt = emptySet();
    assertEmpty(cartesianProduct(mt, set(1)));
  }

  public void testCartesianProduct_binary1x0() {
    Set<Integer> mt = emptySet();