code: @Test public void testBasic(){
    final HeaderValues headerValues=new HeaderValues(Headers.DEFLATE);
    assertEquals(0,headerValues.size());
    assertTrue(headerValues.isEmpty());
    assertFalse(headerValues.iterator().hasNext());
    assertFalse(headerValues.descendingIterator().hasNext());
    assertFalse(headerValues.listIterator().hasNext());
    assertFalse(headerValues.listIterator(0).hasNext());
    assertNull(headerValues.peek());
    assertNull(headerValues.peekFirst());
    assertNull(headerValues.peekLast());
  }
  