---
- import_tasks: setup_value.yml

- name: unsetting value with check mode
  git_config:
    name: "{{ option_name }}"
    scope: "{{ option_scope }}"
    state: absent
  check_mode: yes
  register: unset_result

- name: getting value
  git_config:
    name: "{{ option_name }}"
    scope: "{{ option_scope }}"
  register: get_result

- name: assert unset changed but dit not delete value
  assert:
    that:
      - unset_result is changed
      - unset_result.diff.before == option_value + "\n"
      - unset_result.diff.after == "\n"
      - get_result.config_value == option_value
...