As this question raised on irc I think is time to get some feedback on it.

Molecule is the official Ansible role testing framework which allows testing of Ansible roles (or playbooks) in isolation by taking care care of provisioning and cleanup of the required resources. Most common use-case is to use docker containers to test, where you can start running your role code in a couple of seconds, being able to run in parallel lots of platforms.

Mainly as a role developer (or even occasional contributor), it makes extremely easy to run tests locally*, before even creating a change-request.

So this opens few sub-questions:

a) can we allow people to add molecule files, even if we do not run molecule in check/gates? -- there is value in this, even without jobs. b) can/should we add molecule jobs for these so we can assure they keep running? c) would this create duplication between what is tested as standalone zuul jobs and what what is tested via molecule ones? Is this a reason to worry or not?

These roles are used on multiple zuul server so is in our interest to make them as reusable as possible. Maybe on opendev.org instance we do not have the resources to test them on all possible platforms, but this does not mean that other zuul instances cannot run these tests.

In addition to making a role developer life easier by allowing it to run ansible code in a say similar to running unittests, we can even see other benefits: uploaded CRs would be of better quality and we will also lower zuul load, improving the build-response-time even for users that do not test their changes locally before uploading them.

* Developer can still define DOCKER_HOST=ssh://host and fully avoid the need to install docker locally. So the term "locally" is a bit relaxed, as you can offload the work to external systems. Is more of running tests on my own hardware, but isolated, so I would not mess my localhost.

Thanks Sorin Sbarnea