@BeforeEach
  internal fun setUp() {
    val inetAddresses = InetAddress.getAllByName("localhost")
    localhostIpv4 = inetAddresses.firstOrNull { it is Inet4Address }
      ?: throw TestAbortedException()
    localhostIpv6 = inetAddresses.firstOrNull { it is Inet6Address }
      ?: throw TestAbortedException()

    serverIpv4 = MockWebServer()
    serverIpv4.start(localhostIpv4, 0) // Pick any available port.

        val peekedHeader =
          reader.peekHeader()
            ?: throw ProtocolException("expected a value at $reader")

        val choice =
          choices.firstOrNull { it.matches(peekedHeader) }
            ?: throw ProtocolException(
              "expected a matching choice but was $peekedHeader at $reader",
            )

        return choice to choice.fromDer(reader)