ansible/test/integration/targets/hostname/tasks/test_check_mode.yml

- name: Run hostname module in check_mode
  hostname:
    name: crocodile.ansible.test.doesthiswork.net.example.com
  check_mode: true
  register: hn1

- name: Get current hostname again
  command: hostname
  register: after_hn

- name: Ensure hostname changed properly
  assert:
    that:
      - hn1 is changed
      - original.stdout == after_hn.stdout

- when: _hostname_file is defined and _hostname_file
  block:
    - name: See if current hostname file exists
      stat:
        path: "{{ _hostname_file }}"
      register: hn_stat

    - name: Move the current hostname file if it exists
      command: mv {{ _hostname_file }} {{ _hostname_file }}.orig
      when: hn_stat.stat.exists

    - name: Run hostname module in check_mode
      hostname:
        name: crocodile.ansible.test.doesthiswork.net.example.com
      check_mode: true
      register: hn

    - stat:
        path: /etc/rc.conf.d/hostname
      register: hn_stat_checkmode

    - assert:
        that:
          # TODO: This is a legitimate bug and will be fixed in another PR.
          # - not hn_stat_checkmode.stat.exists
          - hn is changed

    - name: Get hostname again
      command: hostname
      register: current_after_cm

    - assert:
        that:
          - original.stdout == current_after_cm.stdout