ansible/test/integration/targets/delegate_to/resolve_vars.yml

---
- name: though we test for 'vars' this is only for backwards compatibility and the 'vars' variable will be deprecated and removed in the future
  hosts: localhost
  gather_facts: no
  tasks:
    - add_host:
        name: host1
        ansible_connection: local

- hosts: localhost
  gather_facts: no
  vars:
    server_name: host1
  tasks:
    - command: echo should delegate to host1 with local connection
      delegate_to: "{{ vars['server_name'] }}"