Molecule hands on

tags: Documentation

Setup

python3 virtualenv
pip install molecule
pip install molecule[docker]
pip install selinux

  • need docker installed
  • need selinux python
python2-libselinux-2.9-3.1.fc30.x86_64
python3-libselinux-2.9-3.1.fc30.x86_64

Setup part duex

First of all we need to clone tripleo-quickstart

git clone https://opendev.org/openstack/tripleo-quickstart

Go to fetch-images role

cd tripleo-quickstart/roles/fetch-images

Create a molecule scenario inside the role

molecule init scenario -r fetch-images

Expected output:

–> Initializing new scenario default…
Initialized scenario in /var/home/arxcruz/tmp/molecule/tripleo-quickstart/roles/fetch-images/molecule/default successfully.

List the tests

molecule list

Expected output:

--> Validating schema /var/home/arxcruz/tmp/molecule/tripleo-quickstart/roles/fetch-images/molecule/default/molecule.yml.
Validation completed successfully.
Instance Name    Driver Name    Provisioner Name    Scenario Name    Created    Converged
---------------  -------------  ------------------  ---------------  ---------  -----------
instance         docker         ansible             default          false      false

Create docker image

This command will create the container

molecule create

Log into docker

Login into the container

molecule login

Run molecule test

This first run will fail because we have lint enabled that will fail

molecule test

Let's disable the lint for now

vim molecule/default/molecule.yml

---
dependency:
  name: galaxy
driver:
  name: docker
lint:
  name: yamllint
  enabled: false  # <--
platforms:
  - name: instance
    image: centos:7
provisioner:
  name: ansible
  lint:
    name: ansible-lint
    enabled: false  # <--
verifier:
  name: testinfra
  lint:
    name: flake8
    enabled: false  # <--

Steps for each scenario

Okay, now we disable the lint, but you may notice that our tests follow some steps: lint, depedency, cleanup, destroy, syntax, create, etc. We don't need to follow all these steps, in general, what we want is destroy any container that might exist, create again, converge, and then destroy again. We can do it adding a test_sequence in the scenario:

vim molecule/default/molecule.yml

scenario:
  test_sequence:
    - destroy
    - create
    - converge
    - destroy

Let's run the test again:

molecule test 
put here long output here...
....

This time will fail because we don't have the user stack on this image, so let's create the image and add the user

molecule create

Login to the container with

molecule login

Create the user

adduser stack

Exit the container and now let's execute the test again, this time passing the –destroy never

molecule test --destroy never

There's another failure, this time related to images that is not defined, but let's do something else first.

But not only that, this approach works only because we create the container, login into it and manually add the user stack there, if we run it again, without the –destroy never option, it will fail, because the previous container will be destroyed, a new one will be created without the user stack. Solve this is easy, we can just add a new task in our playbook, that will create the user stack. Think this is as the setupClass in python unittest.

So, as you can see, if you run again without the –destroy option, it will fail.

molecule test

Let's create the user in the playbook then

vim molecule/default/playbook.yml

---
- name: Converge
  hosts: all
  tasks:
    - name: Create user stack
      user:
        name: stack
        comment: Stack user
    - name: Execute the role
      include_role:
        name: fetch-images

Let's run again and you will see the user bein created

molecule test

As you can see, there is no longer stack user failures, let's fix now the issue with the images.

In this case, we have a bug in the role, because all the variables used by the role, should be in the defaults/main.yml, thanks to molecule, now we can fix it!

vim defaults/main.yml

images:
  - name: centos-7-image
    url: "http://download.cirros-cloud.net/0.3.4/cirros-0.3.4-x86_64-disk.img"
    type: img
    md5sum: 'ee1eca47dc88f4879d8a229cc70a07c6'

We could also add a different image in the molecule test since we should not rely on internet to run our tests

vim molecule/default/playbook.yml

  - name: Create dummy image file
    copy:
      dest: /tmp/image-test.img
      content: |
        foo

And add the vars:

      vars:
        # This image is not a real image, it's just for
        # test purpose
        images:
          - name: centos-7-image
            url: "file:///tmp/image-test.img"
            type: img
            md5sum: 'd3b07384d113edec49eaa6238ad5ff00'

And we are done, now we have a molecule test covering the fetch-images role!

molecule test

All tests should be executed fine

Select a repo