fix: do not use TestServer in ConnectionStub

It's an internal testing entity, we cannot use it in a test case class

actioncable/lib/action_cable/channel/base.rb

@@ -286,7 +286,7 @@ module ActionCable
         end
 
         def parameter_filter
-          @parameter_filter ||= ActiveSupport::ParameterFilter.new(connection.server.config.filter_parameters)
+          @parameter_filter ||= ActiveSupport::ParameterFilter.new(connection.config.filter_parameters)
         end
 
         def transmit_subscription_confirmation

actioncable/lib/action_cable/channel/test_case.rb

@@ -45,7 +45,7 @@ module ActionCable
     end
 
     class ConnectionStub
-      attr_reader :transmissions, :identifiers, :subscriptions, :logger, :server
+      attr_reader :transmissions, :identifiers, :subscriptions, :logger, :config
 
       def initialize(identifiers = {})
         @transmissions = []
@@ -57,7 +57,7 @@ module ActionCable
         @subscriptions = ActionCable::Connection::Subscriptions.new(self)
         @identifiers = identifiers.keys
         @logger = ActiveSupport::TaggedLogging.new ActiveSupport::Logger.new(StringIO.new)
-        @server = TestServer.new
+        @config = ActionCable::Server::Configuration.new
       end
 
       def transmit(cable_message)

actioncable/lib/action_cable/connection/base.rb

@@ -51,7 +51,7 @@ module ActionCable
       include ActiveSupport::Rescuable
 
       attr_reader :server, :env, :subscriptions, :logger, :worker_pool, :protocol
-      delegate :event_loop, :pubsub, to: :server
+      delegate :event_loop, :pubsub, :config, to: :server
 
       def initialize(server, env, coder: ActiveSupport::JSON)
         @server, @env, @coder = server, env, coder

actioncable/test/stubs/test_connection.rb

@@ -5,7 +5,7 @@ require "stubs/user"
 class TestConnection
   attr_reader :identifiers, :logger, :current_user, :server, :subscriptions, :transmissions
 
-  delegate :pubsub, to: :server
+  delegate :pubsub, :config, to: :server
 
   def initialize(user = User.new("lifo"), coder: ActiveSupport::JSON, subscription_adapter: SuccessAdapter)
     @coder = coder