} else {
      iterator.next();
      assertThrows(UnsupportedOperationException.class, iterator::remove);
    }
    assertInvariants(map);
  }

  public void testValuesRemove() {
    Map<K, V> map;
    try {
      map = makePopulatedMap();
    } catch (UnsupportedOperationException e) {
      return;
    }

    Collection<V> valueCollection = map.values();