- hosts: localhost
  gather_facts: false
  pre_tasks:
  - include_tasks:
      file: tasks/trigger_change.yml
      apply:
        notify: hello

  handlers:
    - name: hello
      set_fact: hello=world

  tasks:
    - name: ensure handler ran
      assert:
        that:
          - hello is defined
          - "hello == 'world'"