Testing Ansible Roles with Molecule

May 26, 2022

Molecule

A test framework for Ansible roles maintained by ansible-community. Molecule supports testing with multiple instances, operating systems and distributions, virtualization providers, test frameworks, and test scenarios.

Installation

Installing with pip can tangle the dependencies of the system Python, so creating a virtual environment with Virtualenv or using a dependency manager like Pipenv or Poetry is recommended.

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# Also installs docker, yamllint, and ansible-lint. (podman, vagrant, azure, hetzner are supported too)
$ pip install molecule[docker,lint] 

Writing Tests

Create the /path/to/role/molecule/default directory. (default is the default scenario. Scenarios with other names can be added.)
Create /path/to/role/molecule/default/molecule.yml and enter the following.

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---
dependency:
  name: galaxy
  options:
    requirements-file: ../../requirements.yml
driver:
  name: docker
platforms:
  - name: instance
    image: docker.io/python:3.6-slim-buster
    pre_build_image: true
provisioner:
  name: ansible
verifier:
  name: ansible
lint: |
  set -e
  yamllint -c ../../.yamllint .
  ansible-lint -c ../../.ansible-lint

Create /path/to/role/molecule/default/converge.yml and add the provisioning code

Insert the code that runs the Role to set up the environment after the docker container is created. (Deploying a web server, etc.)

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---
- name: Converge
  hosts: all
  tasks:
    - include_role:
        name: "myrole"

Create /path/to/role/molecule/default/verify.yml and add the verification code

Insert the code that verifies the environment after it’s set up (this is where the actual testing happens)

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---
- name: Verify
  hosts: all
  gather_facts: false
  tasks:
    - assert:
         that: "{{ condition }}"

Running

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$ cd /path/to/role
$ molecule create # Install dependencies and start the docker container
$ molecule converge # Run converge.yml
$ molecule verify # Run verify.yml
$ molecule destroy # Remove the docker container
$ molecule test # Do all of the above in one shot

Various Terminology Used in the Workplace Ansible Molecule with Kind - Kubernetes Automation Testing with Docker