make own dummy, less confusing what is gem/engine and what is app

dummy/test/channels/application_cable/connection_test.rb

@@ -0,0 +1,11 @@
+require "test_helper"
+
+class ApplicationCable::ConnectionTest < ActionCable::Connection::TestCase
+  # test "connects with cookies" do
+  #   cookies.signed[:user_id] = 42
+  #
+  #   connect
+  #
+  #   assert_equal connection.user_id, "42"
+  # end
+end