OkHttpClient.Builder()
        .protocols(protocols as List<Protocol>)
    }.also { expected ->
      assertThat(expected.message).isEqualTo("protocols must not contain null")
    }
  }

  @Test fun spdy3IsRemovedFromProtocols() {
    val protocols =
      mutableListOf(
        Protocol.HTTP_1_1,
        Protocol.SPDY_3,
      )
    val client =
      OkHttpClient.Builder()

     * Returns the concatenation of 8-bit, length prefixed protocol names.
     * http://tools.ietf.org/html/draft-agl-tls-nextprotoneg-04#page-4
     */
    fun concatLengthPrefixed(protocols: List<Protocol>): ByteArray {
      val result = Buffer()
      for (protocol in alpnProtocolNames(protocols)) {
        result.writeByte(protocol.length)
        result.writeUtf8(protocol)
      }
      return result.readByteArray()
    }

      .assertSuccessful()
      .assertCode(200)
  }

  private fun enableProtocol(protocol: Protocol) {
    enableTls()
    client =
      client.newBuilder()
        .protocols(listOf(protocol, Protocol.HTTP_1_1))
        .build()
    server1.protocols = client.protocols
    server2.protocols = client.protocols
  }

  private fun enableTls() {
    client =
      client.newBuilder()

  }

  @Test
  fun testH2PriorKnowledgeServerFallback() {
    try {
      server.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE, Protocol.HTTP_1_1)
      fail<Unit>()
    } catch (expected: IllegalArgumentException) {
      assertThat(expected.message).isEqualTo(
        "protocols containing h2_prior_knowledge cannot use other protocols: " +
          "[h2_prior_knowledge, http/1.1]",
      )
    }
  }

  @Test

  }

  @Test
  fun testH2PriorKnowledgeServerFallback() {
    try {
      server.protocols = Arrays.asList(Protocol.H2_PRIOR_KNOWLEDGE, Protocol.HTTP_1_1)
      fail<Any>()
    } catch (expected: IllegalArgumentException) {
      assertThat(expected.message).isEqualTo(
        "protocols containing h2_prior_knowledge cannot use other protocols: " +
          "[h2_prior_knowledge, http/1.1]",
      )
    }
  }

  @Test

      response!!.closeQuietly()
    }
  }

  private fun enableHttps() {
    enableHttpsAndAlpn(Protocol.HTTP_1_1)
  }

  private fun enableHttp2() {
    platform.assumeHttp2Support()
    enableHttpsAndAlpn(Protocol.HTTP_2, Protocol.HTTP_1_1)
  }

  private fun enableHttpsAndAlpn(vararg protocols: Protocol) {
    client =
      client.newBuilder()
        .sslSocketFactory(

    }

    /**
     * When [protocols][MockWebServer.protocols] include [HTTP_2][okhttp3.Protocol], this attaches a
     * pushed stream to this response.
     */
    fun addPush(promise: PushPromise) =
      apply {
        this.pushPromises += promise
      }

    /**
     * When [protocols][MockWebServer.protocols] include [HTTP_2][okhttp3.Protocol], this pushes

    val dns: Dns = address.dns()
    val socketFactory: SocketFactory = address.socketFactory()
    val proxyAuthenticator: Authenticator = address.proxyAuthenticator()
    val protocols: List<Protocol> = address.protocols()
    val connectionSpecs: List<ConnectionSpec> = address.connectionSpecs()
    val proxySelector: ProxySelector = address.proxySelector()
    val proxy: Proxy? = address.proxy()

   */
  var protocols: List<Protocol> = immutableListOf(Protocol.HTTP_2, Protocol.HTTP_1_1)
    set(value) {
      val protocolList = value.toImmutableList()
      require(Protocol.H2_PRIOR_KNOWLEDGE !in protocolList || protocolList.size == 1) {
        "protocols containing h2_prior_knowledge cannot use other protocols: $protocolList"
      }

    dnsResults =
      listOf(
        localhostIpv4,
        localhostIpv6,
        TestUtil.UNREACHABLE_ADDRESS_IPV4.address,
      )
    serverIpv4.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)
    serverIpv6.protocols = listOf(Protocol.H2_PRIOR_KNOWLEDGE)

    // Yield the first IP address so the second IP address completes first.
    val firstConnectLatch = CountDownLatch(1)
    val socketFactory =