ansible/test/integration/targets/roles/no_dupes.yml

- name: play should only show 1 invocation of a, as dependencies in this play are deduped
  hosts: testhost
  gather_facts: false
  tags: [ 'inroles' ]
  roles:
    - role: a
    - role: b
    - role: c

- name: play should only show 1 invocation of a, as dependencies in this play are deduped even outside of roles
  hosts: testhost
  gather_facts: false
  tags: [ 'acrossroles' ]
  roles:
    - role: a
    - role: b
  tasks:
    - name: execute role c which depends on a
      import_role: name=c