One to read: “Test Driven Development (TDD) for networks, using Ansible”

Thanks to my colleague Simon (@sipart on Twitter), I spotted this post (and it’s companion Github Repository) which explains how to do test-driven development in Ansible.

Essentially, you create two roles – test (the author referred to it as “validate”) and one to actually do the thing you want it to do (in the author’s case “add_vlan”).

In the testing role, you’d have the following layout:

/path/to/roles/testing/tasks/main.yml
/path/to/roles/testing/tasks/SOMEFEATUREtest.yml

In the main.yml file, you have a simple stanza:

---
- name: Include all the test files
  include: "{{ outer_item }}"
  with_fileglob:"/path/to/roles/validate/tasks/*test.yml"
  loop_control: loop_var=outer_item

I’m sure that “with_fileglob” line could be improved to not actually need a full path… anyway

Then in your YourFeature_test.yml file, you do things like this:

---
- name: "Pseudocode in here. Use real modules for your testing!!"
  get_vlan_config: filter_for=needle_vlan
  register:haystack_var

- assert: that=" {{ needle_item }} in haystack_var "

When you run the play of the role the first time, the response will be “failed” (because “needle_vlan” doesn’t exist). Next do the “real” play of the role (so, in the author’s case, add_vlan) which creates the vlan. Then re-run the test role, your response should now be “ok”.

I’d probably script this so that it goes:

      reset-environment set_testing=true (maybe create a random little network)
      test
      run-action
      test
      reset-environment set_testing=false

The benefit to doing it that way is that you “know” your tests aren’t running if the environment doesn’t have the “set_testing” thing in place, you get to run all your tests in a “clean room”, and then you clear it back down again afterwards, leaving it clear for the next pass of your automated testing suite.

Fun!

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