results.log

 1) test Initates a connection proper. (Phoenix.Router.RawWebsocketHandlerTest)
     ** (UndefinedFunctionError) undefined function: Socket.TCP.packet!/2
     stacktrace:
       Socket.TCP.packet!(:raw, {Socket.TCP, #Port<0.20319>, nil, {:resource, 305923944, ""}})
       lib/socket/web.ex:210: Socket.Web.connect!/3
       lib/socket/web.ex:140: Socket.Web.connect/3
       test/phoenix/websocket_handler_test.exs:24: Phoenix.Router.RawWebsocketHandlerTest."test Initates a connection proper."/1

test.exs

defmodule Phoenix.Router.RawWebsocketHandlerTest do
  use ExUnit.Case
  use PlugHelper

  defmodule EchoHandler do
    use Phoenix.Websocket.RawHandler

    def stream(data, socket, _state) do
      reply socket, data
    end
  end

  defmodule Router do
    use Phoenix.Router, port: 5000
    raw_websocket "/echo", EchoHandler
  end

  setup do
    {:ok, server: Router.start}
  end

  test "Initates a connection proper." do
    {:ok, sock} = Socket.Web.connect("localhost", 5000, path: "/echo")
  end

  teardown meta do
    meta[:server].stop
  end
end

Hi, knewter.
I met same problem. Do you have any solutions?