How to use assert module in Ansible?

I want an Ansible code that asserts and checks these two interfaces are not equal:

bond_interfaces: [eno5, eno6]

node0125.computer.me: 
          management_ip: x.x.x.x
          management_interface: ens3f0
          bond_interfaces: [eno5, eno6]
          private_ip: x.x.x.x
          # ilo_ip: x.x.x.x
          ansible_host: '{{ management_ip }}'
          tier: balanced
          os_version: 20.04

Solution

According the documentation of assert module – Asserts given expressions are true a minimal example playbook could look like

---
- hosts: localhost
  become: false
  gather_facts: false

  vars:

    node0125_compute_neda: 
      bond_interfaces: [eno5, eno6]

  tasks:

  - assert:
      that:
        - node0125_compute_neda.bond_interfaces[0] != node0125_compute_neda.bond_interfaces[1]
      fail_msg: "Network bond is not over two different interfaces"

resulting into an output of

TASK [assert] ******************
ok: [localhost] => changed=false
  msg: All assertions passed

or if on the same interface

TASK [assert] ******************************************************************************************************************************************
fatal: [localhost]: FAILED! => changed=false
  assertion: node0125_compute_neda.bond_interfaces[0] != node0125_compute_neda.bond_interfaces[1]
  evaluated_to: false
  msg: Network bond is not over two different interfaces

Since bond_interfaces: [eno5, eno6] is a list with two elements, the check will assure that the first list element is not equal the second list element.

If the list will have only two elements, it would also be possible to compare the first with the last element.

  - assert:
      that:
        - node0125_compute_neda.bond_interfaces | length == 2
        - node0125_compute_neda.bond_interfaces | first != node0125_compute_neda.bond_interfaces | last
      fail_msg: "Network bond is not over two different interfaces"