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

dummy/test/application_system_test_case.rb

@@ -0,0 +1,5 @@
+require "test_helper"
+
+class ApplicationSystemTestCase < ActionDispatch::SystemTestCase
+  driven_by :selenium, using: :chrome, screen_size: [1400, 1400]
+end

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

dummy/test/test_helper.rb

@@ -0,0 +1,13 @@
+ENV["RAILS_ENV"] ||= "test"
+require_relative "../config/environment"
+require "rails/test_help"
+
+class ActiveSupport::TestCase
+  # Run tests in parallel with specified workers
+  parallelize(workers: :number_of_processors)
+
+  # Setup all fixtures in test/fixtures/*.yml for all tests in alphabetical order.
+  fixtures :all
+
+  # Add more helper methods to be used by all tests here...
+end