create new integration test file for flash related tests

test/integration/flash_test.rb

@@ -0,0 +1,9 @@
+require 'test_helper'
+
+class FlashTest < ActionController::IntegrationTest
+  test 'require_no_authentication should set the already_authenticated flash message' do
+    sign_in_as_user
+    visit new_user_session_path
+    assert_equal flash[:alert], I18n.t("devise.failure.already_authenticated")
+  end
+end