forum-1.x-dev/tests/modules/forum_url_alter_test/forum_url_alter_test.services.yml

services:
  forum_url_alter_test.path_processor:
    class: Drupal\forum_url_alter_test\TestPathProcessor
    tags:
      - { name: path_processor_inbound, priority: 800 }
      - { name: path_processor_outbound, priority: 100 }