Add socket authentication tests

lib/chess_web/channels/user_socket.ex

@@ -29,6 +29,7 @@ defmodule ChessWeb.UserSocket do
         :error
     end
   end
+  def connect(%{}, socket), do: :error
 
   # Socket id's are topics that allow you to identify all sockets for a given user:
   #

test/chess_web/channels/user_socket_test.exs

@@ -0,0 +1,20 @@
+defmodule ChessWeb.UserSocketTest do
+  use ChessWeb.ChannelCase, async: true
+
+  alias ChessWeb.UserSocket
+
+  test "authenticate with valid token" do
+    token = Phoenix.Token.sign(@endpoint, "game socket", 42)
+
+    assert {:ok, socket} = connect(UserSocket, %{"token" => token})
+    assert socket.assigns.current_user_id == 42
+  end
+
+  test "cannot authenticate with invalid token" do
+    assert :error = connect(UserSocket, %{"token" => "invalid-token"})
+  end
+
+  test "cannot authenticate with no token" do
+    assert :error = connect(UserSocket, %{})
+  end
+end