{
      Entry<Integer, String> entry = unmod.firstEntry();
      assertThrows(UnsupportedOperationException.class, () -> entry.setValue("four"));
    }
    {
      Entry<Integer, String> entry = unmod.lastEntry();
      assertThrows(UnsupportedOperationException.class, () -> entry.setValue("four"));
    }
    {
      @SuppressWarnings("unchecked")