- hosts: host1
  tasks:
    - name: Assert hostvar is present.
      assert:
        that:
          - allvar == 'all'
          - hostvar == 'host'
          - groupvar is not defined

- hosts: host2
  tasks:
    - name: Assert groupvar is present.
      assert:
        that:
          - allvar == 'all'
          - hostvar is not defined
          - groupvar == 'group'

- hosts: host3
  tasks:
    - name: Assert groupvar is present.
      assert:
        that:
          - allvar == 'all'
          - hostvar is not defined
          - groupvar == 'group'