Proposal: Charm testing for 2.0

[Marco Ceppi]

On Thu, Mar 17, 2016 at 8:24 AM Merlijn Sebrechts <
merlijn.sebrechts at gmail.com> wrote:

> As an aside; is there a good write-up somewhere about charm unit testing.
> I'd like to do this but I'm not sure how to do this. I am completely new to
> unit testing so I'm having a hard time to see how a good unittest for a
> Charm would look like and what exactly should be tested.
>

This is a great question. There's a bug currently open against the reactive
framework to figure out how to build a good set of unittest helpers to make
writing tests really straight forward. As far as a current examples, I
don't have any at the moment - but I will try to find some and if I can't I
will make some!


> 2016-03-17 1:52 GMT+01:00 Marco Ceppi <marco.ceppi at canonical.com>:
>
>> Hello everyone!
>>
>> This is an email I've been meaning to write for a while, and have
>> rewritten a few times now. With 2.0 on the horizon and the charm ecosystem
>> rapidly growing, I couldn't keep the idea to myself any longer.
>>
>> # tl;dr:
>>
>> We should stop writing Amulet tests in charms and instead only write them
>> Bundles and force charms to do unit-testing (when possible) and promote
>> that all charms be included in bundles in the store.
>>
>> # Problem
>>
>> Without making this a novel, charm-testing and amulet started before
>> bundles were even a construct in Juju with a spec written before Juju 1.0.
>> Since then, many new comers to the ecosystem have remarked how odd it is to
>> be writing deployment validations at the charm level. Indeed, as years have
>> gone by and new tools have sprung up it's become clear that; having an
>> author try to model all the permutations of a charms deployment and do the
>> physical deploys at that charm level are tedious and incomplete at best.
>>
>> With the explosion of layers and improvements to uniting test in charms
>> at that component level, I feel that continuing to create these bespoke
>> "bundles" via amulet in a single charm will not be a robust solution going
>> forward. As we sprint closer to Juju 2.0 we're seeing a higher demand for
>> assurance of working scenarios, and a sharp focus on quality at every
>> level. As such I'd like to propose the following policy changes:
>>
>> - All bundles must have tests before promulgation to the store
>> - All charms need to have comprehensive tests (unit or amulet)
>> - All charms should be included in a bundle
>>
>> I'll break down my reasoning and examples in the following sections:
>>
>> # All bundles must have tests before promulgation to the store
>>
>> Writing bundle tests with Amulet is actually a more compelling story
>> today than writing an Amulet test case for a charm. As an example, there's
>> a new ELK stack bundle being produced, here's what the test for that bundle
>> looks like:
>> https://github.com/juju-solutions/bundle-elk-stack/blob/master/tests/10-test-bundle
>>
>> This makes a lot of sense because it's asserting that the bundle is
>> working as expected by the Author who put the bundle together. It's also
>> loading the bundle.yaml as the deployment spec meaning as the bundle
>> evolves the tests will make sure they continue to run as expected. Also,
>> this could potentially be used in future smoke tests for charms being
>> updated if a CI process swaps out, say elasticsearch, for a newer version
>> of a charm being reviewed. We can assert that both the unittests in
>> elasticsearch work and it operates properly in an existing real world
>> solution a la the bundle.
>>
>> Additional examples:
>> -
>> https://github.com/juju-solutions/bundle-realtime-syslog-analytics/blob/master/tests/01-bundle.py
>> -
>> https://github.com/juju-solutions/bundle-apache-core-batch-processing/blob/master/tests/01-bundle.py
>>
>> # All charms need to have comprehensive tests (unit or amulet)
>>
>> This is just a clarification and more strongly typed policy change that
>> require charms have (preferred) unit tests or, if not applicable, then an
>> Amulet test. Bash doesn't really allow for unittesting, so in those
>> scenarios, Amulet tests would function as a valid testing case.
>>
>> There are also some charms which will not make sense as a bundle. One
>> example is the recently promulgated Fiche charm:
>> http://bazaar.launchpad.net/~charmers/charms/trusty/fiche/trunk/view/head:/tests/10-deploy It's
>> a standalone pastebin, but it's an awesome service that provides deployment
>> validation with an Amulet test. The test stands up the charm, exercises
>> configuration, and validates the service responds in an expected way. For
>> scenarios where a charm does not have a bundle an Amulet test would be
>> required.
>>
>> Any charm that currently includes an Amulet test is welcome to continue
>> keeping such a test.
>>
>> # All charms should be included in a bundle
>>
>> This last one is to underscore that charms need to serve a purpose. This
>> policy is written as not an absolute, but instead a strongly worded
>> suggestion as there are always charms that are exceptions to the rules. One
>> such example is the aforementioned Fiche charm which as a bundle would not
>> make as much sense, but is still a purposeful charm.
>>
>> That being said, most users coming to consume Juju are looking to solve a
>> problem. Bundles underscore solutions to problems that people can consume,
>> and get started quicker.
>>
>> As such, when new applications are charmed a test of "is this application
>> something that serves a clear purpose" having a bundle submitted alongside
>> the charm validates that claim and provides users a way to immediately get
>> started with a solution.
>>
>> # Conclusion
>>
>> These policy changes, once accepted, will be targeted at all charms and
>> bundles in Xenial as well as any new charm submitted after policy
>> acceptance date for trusty, and finally any charm currently under review
>> will be encouraged to adhere to the new policy but won't be required.
>>
>> # Action items
>>
>> I'm seeking feedback on this concept and welcome suggestions for
>> improvements, questions, dissenting opinions, and any other remarks as well
>> as votes from ~charmers and feedback from the community at large.
>>
>> Thanks,
>> Marco Ceppi
>>
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>>
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