rules-8.x-3.x-dev/tests/modules/rules_test_ui_embed/rules_test_ui_embed.routing.yml

rules_test_ui_embed.settings:
  path: '/admin/config/user-interface/css'
  defaults:
    _form: '\Drupal\rules_test_ui_embed\Form\SettingsForm'
    _title: 'CSS rules'
  requirements:
    _permission: 'administer rules'
  options:
    _rules_ui: rules_test_ui_embed.settings_conditions