var duration time.Duration
	switch timePart {
	case timePartYear:
		return FromTimestamp(t.AddDate(int(qty), 0, 0)), nil
	case timePartMonth:
		return FromTimestamp(t.AddDate(0, int(qty), 0)), nil
	case timePartDay:
		return FromTimestamp(t.AddDate(0, 0, int(qty))), nil
	case timePartHour:
		duration = time.Duration(qty) * time.Hour
	case timePartMinute:

        }
    }

    public static void addBefore(Element sibling, Node n) {
        def parent = sibling.parentNode
        parent.insertBefore(n, sibling)
    }

    public static Object addAfter(Element sibling, Closure cl) {
        DomBuilder builder = new DomBuilder(sibling.ownerDocument, null)
        cl.delegate = builder
        cl.call()
        def parent = sibling.parentNode

    ).isEqualTo(10L)
    assertThat(
      Headers
        .Builder()
        .add("abc", "def")
        .add("ghi", "jkl")
        .build()
        .byteCount(),
    ).isEqualTo(20L)
  }

  @Test fun addDate() {
    val expected = Date(0L)
    val headers =
      Headers
        .Builder()
        .add("testDate", expected)
        .build()
    assertThat(headers["testDate"]).isEqualTo("Thu, 01 Jan 1970 00:00:00 GMT")