I previously walked through Ansible role creation with Molecule, but it’s just as easy to add to existing roles. Creating a Molecule scenario to test an existing role allows for easy testing and modification of that role with all the benefits that Molecule provides.
Existing role
For another easy example, we’ll just use a simple role that installs a webserver. To prevent a complete copy/paste, this time we will be using Apache rather than Nginx. To show the existing role in its current state:
~/Projects/example_playbooks/apache_install$ tree
.
└── tasks
└── main.yml
1 directory, 1 file
~/Projects/example_playbooks/apache_install$ cat tasks/main.yml
---
# install and start apache
- name: install apache
yum:
name: httpd
state: present
become: "yes"
- name: ensure apache running and enabled
systemd:
name: httpd
state: started
enabled: "yes"
become: "yes"
The Molecule and Ansible version used for this example is:
~/Projects/example_playbooks/apache_install$ ansible --version && molecule --version
ansible 2.6.4
config file = /etc/ansible/ansible.cfg
configured module search path = [u'/home/dan/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
ansible python module location = /home/dan/.local/lib/python2.7/site-packages/ansible
executable location = /home/dan/.local/bin/ansible
python version = 2.7.12 (default, Dec 4 2017, 14:50:18) [GCC 5.4.0 20160609]
molecule, version 2.17.0
Init scenario
Because the role already exists, we will only be creating scenario, rather than a whole new role. The init scenario parameters are almost exactly the same as init role, and result in the same directory structure as if we created the role with molecule.
Molecule init scenario usage information:
~/Projects/example_playbooks/apache_install$ molecule init scenario --help
Usage: molecule init scenario [OPTIONS]
Initialize a new scenario for use with Molecule.
Options:
--dependency-name [galaxy] Name of dependency to initialize. (galaxy)
-d, --driver-name [azure|delegated|docker|ec2|gce|lxc|lxd|openstack|vagrant]
Name of driver to initialize. (docker)
--lint-name [yamllint] Name of lint to initialize. (ansible-lint)
--provisioner-name [ansible] Name of provisioner to initialize. (ansible)
-r, --role-name TEXT Name of the role to create. [required]
-s, --scenario-name TEXT Name of the scenario to create. (default)
[required]
--verifier-name [goss|inspec|testinfra]
Name of verifier to initialize. (testinfra)
--help Show this message and exit.
We create the scenario using the existing role name and specifying using vagrant as the driver. Once initialized, the Molecule directory structure will be the same as if we created the role with Molecule, but without any role directories being created (such as handlers, meta, etc).
~/Projects/example_playbooks/apache_install$ molecule init scenario --role-name apache_install --driver-name vagrant
--> Initializing new scenario default...
Initialized scenario in /home/dan/Projects/example_playbooks/apache_install/molecule/default successfully.
~/Projects/example_playbooks/apache_install$ tree
.
├── molecule
│ └── default
│ ├── INSTALL.rst
│ ├── molecule.yml
│ ├── playbook.yml
│ ├── prepare.yml
│ └── tests
│ └── test_default.py
└── tasks
└── main.yml
4 directories, 6 files
Configuration
The Molecule configuration will be the default provided by molecule. As done previously, I edit this to use CentOS 7, rather than the default Ubuntu 16.04. Additionally, I update the name of the VM to something different to distinguish the VM if needed.
In this example our tests are very similiar to my previous example. The primary (and possibly only) differences in our tests from the previous example is we’re testing for the httpd service rather than nginx.
~/Projects/example_playbooks/apache_install$ cat molecule/default/molecule.yml
---
dependency:
name: galaxy
driver:
name: vagrant
provider:
name: virtualbox
lint:
name: yamllint
platforms:
- name: apache
box: centos/7
provisioner:
name: ansible
lint:
name: ansible-lint
scenario:
name: default
verifier:
name: testinfra
lint:
name: flake8
~/Projects/example_playbooks/apache_install$ cat molecule/default/tests/test_default.py
import os
import testinfra.utils.ansible_runner
testinfra_hosts = testinfra.utils.ansible_runner.AnsibleRunner(
os.environ['MOLECULE_INVENTORY_FILE']).get_hosts('all')
def test_apache_installed(host):
apache = host.package("httpd")
assert apache.is_installed
def test_apache_config(host):
apache = host.file('/etc/httpd/conf/httpd.conf')
assert apache.exists
def test_apache_running_and_enabled(host):
apache = host.service("httpd")
assert apache.is_running
assert apache.is_enabled
Molecule test
Since we’ve updated our Molecule configuration to use the Vagrant box we want, and updated our tests to ensure that our role is doing what we want, we can now run any of the Molecule commands (test, create, converge, etc) just as we would if we would have started the role using Molecule.
~/Projects/example_playbooks/apache_install$ molecule test
--> Validating schema /home/dan/Projects/example_playbooks/apache_install/molecule/default/molecule.yml.
Validation completed successfully.
--> Test matrix
└── default
├── lint
├── destroy
├── dependency
├── syntax
├── create
├── prepare
├── converge
├── idempotence
├── side_effect
├── verify
└── destroy
--> Scenario: 'default'
--> Action: 'lint'
--> Executing Yamllint on files found in /home/dan/Projects/example_playbooks/apache_install/...
Lint completed successfully.
--> Executing Flake8 on files found in /home/dan/Projects/example_playbooks/apache_install/molecule/default/tests/...
Lint completed successfully.
--> Executing Ansible Lint on /home/dan/Projects/example_playbooks/apache_install/molecule/default/playbook.yml...
Lint completed successfully.
--> Scenario: 'default'
--> Action: 'destroy'
PLAY [Destroy] *****************************************************************
TASK [Destroy molecule instance(s)] ********************************************
changed: [localhost] => (item=None)
changed: [localhost]
TASK [Populate instance config] ************************************************
ok: [localhost]
TASK [Dump instance config] ****************************************************
changed: [localhost]
PLAY RECAP *********************************************************************
localhost : ok=3 changed=2 unreachable=0 failed=0
--> Scenario: 'default'
--> Action: 'dependency'
Skipping, missing the requirements file.
--> Scenario: 'default'
--> Action: 'syntax'
playbook: /home/dan/Projects/example_playbooks/apache_install/molecule/default/playbook.yml
--> Scenario: 'default'
--> Action: 'create'
PLAY [Create] ******************************************************************
TASK [Create molecule instance(s)] *********************************************
changed: [localhost] => (item=None)
changed: [localhost]
TASK [Populate instance config dict] *******************************************
ok: [localhost] => (item=None)
ok: [localhost]
TASK [Convert instance config dict to a list] **********************************
ok: [localhost]
TASK [Dump instance config] ****************************************************
changed: [localhost]
PLAY RECAP *********************************************************************
localhost : ok=4 changed=2 unreachable=0 failed=0
--> Scenario: 'default'
--> Action: 'prepare'
PLAY [Prepare] *****************************************************************
TASK [Install python for Ansible] **********************************************
ok: [apache]
PLAY RECAP *********************************************************************
apache : ok=1 changed=0 unreachable=0 failed=0
--> Scenario: 'default'
--> Action: 'converge'
PLAY [Converge] ****************************************************************
TASK [Gathering Facts] *********************************************************
ok: [apache]
TASK [apache_install : install apache] *****************************************
changed: [apache]
TASK [apache_install : ensure apache running and enabled] **********************
changed: [apache]
PLAY RECAP *********************************************************************
apache : ok=3 changed=2 unreachable=0 failed=0
--> Scenario: 'default'
--> Action: 'idempotence'
Idempotence completed successfully.
--> Scenario: 'default'
--> Action: 'side_effect'
Skipping, side effect playbook not configured.
--> Scenario: 'default'
--> Action: 'verify'
--> Executing Testinfra tests found in /home/dan/Projects/example_playbooks/apache_install/molecule/default/tests/...
============================= test session starts ==============================
platform linux2 -- Python 2.7.12, pytest-3.3.1, py-1.5.2, pluggy-0.6.0
rootdir: /home/dan/Projects/example_playbooks/apache_install/molecule/default, inifile:
plugins: testinfra-1.14.1
collected 3 items
tests/test_default.py ... [100%]
=========================== 3 passed in 5.62 seconds ===========================
Verifier completed successfully.
--> Scenario: 'default'
--> Action: 'destroy'
PLAY [Destroy] *****************************************************************
TASK [Destroy molecule instance(s)] ********************************************
changed: [localhost] => (item=None)
changed: [localhost]
TASK [Populate instance config] ************************************************
ok: [localhost]
TASK [Dump instance config] ****************************************************
changed: [localhost]
PLAY RECAP *********************************************************************
localhost : ok=3 changed=2 unreachable=0 failed=0
Conclusion
Molecule not only provides great defaults and a consistent directory structure when creating a new role, but also makes it easy and efficient to add a Molecule workflow for testing existing roles. Adding Molecule scenarios to existing roles is simple and efficient for testing existing roles across Operating Systems and Ansible versions to improve their reliability.
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