Using docker containers

Below you can see a scenario that is using docker containers as test hosts. When you run molecule test --scenario-name docker the create, converge and destroy steps will be run one after another.

This example is using Ansible playbooks and it does not need any molecule plugins to run. You can fully control which test requirements you need to be installed.

Config playbook

molecule.yml

dependency:
  name: galaxy
  options:
    requirements-file: requirements.yml
platforms:
  - name: molecule-ubuntu
    image: ubuntu:18.04

requirements.yml

collections:
  - community.docker

Create playbook

create.yml

- name: Create
  hosts: localhost
  gather_facts: false
  vars:
    molecule_inventory:
      all:
        hosts: {}
        molecule: {}
  tasks:
    - name: Create a container
      community.docker.docker_container:
        name: "{{ item.name }}"
        image: "{{ item.image }}"
        state: started
        command: sleep 1d
        log_driver: json-file
      register: result
      loop: "{{ molecule_yml.platforms }}"

    - name: Print some info
      ansible.builtin.debug:
        msg: "{{ result.results }}"

    - name: Fail if container is not running
      when: >
        item.container.State.ExitCode != 0 or
        not item.container.State.Running
      ansible.builtin.include_tasks:
        file: tasks/create-fail.yml
      loop: "{{ result.results }}"
      loop_control:
        label: "{{ item.container.Name }}"

    - name: Add container to molecule_inventory
      vars:
        inventory_partial_yaml: |
          all:
            children:
              molecule:
                hosts:
                  "{{ item.name }}":
                    ansible_connection: community.docker.docker
      ansible.builtin.set_fact:
        molecule_inventory: >
          {{ molecule_inventory | combine(inventory_partial_yaml | from_yaml, recursive=true) }}
      loop: "{{ molecule_yml.platforms }}"
      loop_control:
        label: "{{ item.name }}"

    - name: Dump molecule_inventory
      ansible.builtin.copy:
        content: |
          {{ molecule_inventory | to_yaml }}
        dest: "{{ molecule_ephemeral_directory }}/inventory/molecule_inventory.yml"
        mode: "0600"

    - name: Force inventory refresh
      ansible.builtin.meta: refresh_inventory

    - name: Fail if molecule group is missing
      ansible.builtin.assert:
        that: "'molecule' in groups"
        fail_msg: |
          molecule group was not found inside inventory groups: {{ groups }}
      run_once: true # noqa: run-once[task]

# we want to avoid errors like "Failed to create temporary directory"
- name: Validate that inventory was refreshed
  hosts: molecule
  gather_facts: false
  tasks:
    - name: Check uname
      ansible.builtin.raw: uname -a
      register: result
      changed_when: false

    - name: Display uname info
      ansible.builtin.debug:
        msg: "{{ result.stdout }}"

tasks/create-fail.yml

- name: Retrieve container log
  ansible.builtin.command:
    cmd: >-
      {% raw %}
      docker logs
      {% endraw %}
      {{ item.stdout_lines[0] }}
  changed_when: false
  register: logfile_cmd

- name: Display container log
  ansible.builtin.fail:
    msg: "{{ logfile_cmd.stderr }}"

Converge playbook

converge.yml

- name: Fail if molecule group is missing
  hosts: localhost
  tasks:
    - name: Print some info
      ansible.builtin.debug:
        msg: "{{ groups }}"

    - name: Assert group existence
      ansible.builtin.assert:
        that: "'molecule' in groups"
        fail_msg: |
          molecule group was not found inside inventory groups: {{ groups }}

- name: Converge
  hosts: molecule
  # We disable gather facts because it would fail due to our container not
  # having python installed. This will not prevent use from running 'raw'
  # commands. Most molecule users are expected to use containers that already
  # have python installed in order to avoid notable delays installing it.
  gather_facts: false
  tasks:
    - name: Check uname
      ansible.builtin.raw: uname -a
      register: result
      changed_when: false

    - name: Print some info
      ansible.builtin.assert:
        that: result.stdout | regex_search("^Linux")

Destroy playbook

destroy.yml

- name: Destroy molecule containers
  hosts: molecule
  gather_facts: false
  tasks:
    - name: Stop and remove container
      delegate_to: localhost
      community.docker.docker_container:
        name: "{{ inventory_hostname }}"
        state: absent
        auto_remove: true

- name: Remove dynamic molecule inventory
  hosts: localhost
  gather_facts: false
  tasks:
    - name: Remove dynamic inventory file
      ansible.builtin.file:
        path: "{{ molecule_ephemeral_directory }}/inventory/molecule_inventory.yml"
        state: absent