.build()
    }

    companion object {
      /** Synthetic response header: the local time when the request was sent. */
      private val SENT_MILLIS = "${Platform.get().getPrefix()}-Sent-Millis"

      /** Synthetic response header: the local time when the response was received. */
      private val RECEIVED_MILLIS = "${Platform.get().getPrefix()}-Received-Millis"
    }
  }

      .assertHeader("a\tb", "c\u007fd")
      .assertHeader("\ud83c\udf69", "\u2615\ufe0f")
      .assertHeader("", "ef")
  }

  @Test
  fun customDns() {
    // Configure a DNS that returns our local MockWebServer for android.com.
    val dns = FakeDns()
    dns["android.com"] = Dns.SYSTEM.lookup(server.url("/").host)
    client =
      client.newBuilder()
        .dns(dns)
        .build()