.add("A", "a")
        .addAll(sourceHeaders)
        .add("C", "c")
        .build()
    assertThat(headers.toString()).isEqualTo("A: a\nA: aa\na: aa\nB: bb\nC: c\n")
  }

  @Test fun nameIndexesAreStrict() {
    val headers = headersOf("a", "b", "c", "d")
    assertFailsWith<IndexOutOfBoundsException> {
      headers.name(-1)
    }
    assertThat(headers.name(0)).isEqualTo("a")