assertThat(copy).containsExactly(0, 1).inOrder();
  }

  public void testNewSetFromMapIllegal() {
    Map<Integer, Boolean> map = new LinkedHashMap<>();
    map.put(2, true);
    try {
      Sets.newSetFromMap(map);
      fail();
    } catch (IllegalArgumentException expected) {
    }
  }

  /** The 0-ary cartesian product is a single empty list. */