Testing HWRPs


#1

Curious if there’s a best practice for testing HWRPs?

The jenkins cookbook is a great example of using HWRPs. I’m wondering how to properly write tests for those. A couple of options came to mind:

  1. Write custom chefspec matchers and test with ChefSpec.
  2. Test resource/provider methods with RSpec.

Thanks,
Curtis


#2

I’ve been down this rabbit hole quite a bit trying to figure this out as
well over the last couple weeks. I haven’t found one happy path, but here
are some suggestions:

First place to look is chef itself. Base chef resources/providers are
written as HWRPs and tested as part of chef.

I tried to leverage ChefSpec matchers by writing an HWRP using the recipe
DSL (https://gist.github.com/bytheway/8672304):

template “foo” do …

instead of

Chef:Resource::Template.new(“foo”)

Not sure how widely known it is, but the Chef::Provider class includes the
same DSL as recipe files, so you can write things this way. The issue I
ran into is that in writing with the DSL, you basically have reverted back
to the behavior of LWRPs before the use_inline_resources declaration was
introduced. Any resources created by the DSL are added to the run_list
after your custom HWRP resource, which might not be the behavior you want.
Your HWRP can call run_action directly on the resource as you create them,
but they are still added to the run list, and looked at to see if they need
to be run again, after your HWRP provider run is complete.

I’ve really liked the idea of the Medium-Weight RP that the splunk cookbook
used (
https://github.com/opscode-cookbooks/chef-splunk/blob/master/libraries/splunk_app_provider.rb)
as a way to make a more testable LWRP. Currently it is hard to unit test
LWRPs because Chef only initializes them as needed at runtime, and even
reloads them if they are already loaded, which makes stubbing out methods
more difficult. (Though, I have found an good way to stub LWRP methods in
ChefSpec: https://gist.github.com/bytheway/9475815)

There aren’t many examples, but a big drawback in most of the cookbooks I
have found with tested HWRPs is that they end up stubbing and mocking a
whole lot of stuff, to the point that you start wondering how brittle they
are.

If your custom resource/provider is mostly just wrapping a bunch of already
existing chef resources, then I’d suggest going with an LWRP or MWRP.
If they are more low level, with very minimal resource re-use, like the
resources/providers defined by Chef itself, I’d suggest you get out your
mocking hat and use Chef source as the guide for how to test.

-Ben

On Mon, Mar 10, 2014 at 3:40 PM, Stewart, Curtis cstewart@momentumsi.comwrote:

Curious if there’s a best practice for testing HWRPs?

The jenkins cookbook is a great example of using HWRPs. I’m wondering
how to properly write tests for those. A couple of options came to mind:

  1. Write custom chefspec matchers and test with ChefSpec.
  2. Test resource/provider methods with RSpec.

Thanks,
Curtis