ansible/test/integration/targets/gathering/explicit.yml

- hosts: testhost
  tasks:
    - name: ensure facts have not been collected
      assert:
        that:
            - ansible_facts is undefined or not 'fqdn' in ansible_facts

- hosts: testhost
  gather_facts: True
  tasks:
    - name: ensure facts have been collected
      assert:
        that:
            - ansible_facts is defined and 'fqdn' in ansible_facts