assertThat(pairs).containsExactly("a" to "b", "c" to "d")
  }

  @Test fun builderGetOperator() {
    val builder = Headers.Builder()
    builder.add("a", "b")
    builder.add("c", "d")
    assertThat(builder["a"]).isEqualTo("b")
    assertThat(builder["c"]).isEqualTo("d")
    assertThat(builder["e"]).isNull()
  }

  @Test fun builderSetOperator() {
    val builder = Headers.Builder()
    builder["a"] = "b"