Breaking down bundle exec rake spec
What is happening when you run:
The first command you are running is bundle. Bundle is kinda like virtualenv for Ruby. It makes sure that you use the same ruby libraries that you, everyone, and puppetmasters use.
Bundle uses a Gemfile, and searches downwards. As long as you have the Gemfile in the puppet repo, it will work.
The second part is exec. Exec is an argument to bundle, it simply means run a command. Because you are running it in a “bundled” environment, it runs the next command that is part of your bundle, with the ruby libraries in your Gemfile.
The third part is rake. Rake is like Make for Ruby. It requires a Rakefile. Each puppet module needs a Rakefile.
You don’t need to re-invent the Rakefile, simply have this in it:
This ensures that we are all running tests in the same way.
Spec is a “rake task” that runs Rspec. Rspec is a ruby testing framework. Rspec + puppet-rspec is a whole other thing described Next Section.
How does Rspec Test Puppet Code?
If you are running bundle exec rake spec, rspec takes over in the environment provided by bundler. It gives you all the gems necissary to do the job, but how does Rspec know about Puppet Code?
If you are including the puppetlabs_spec_helper/rake_tasks, your exact task includes the prep/test/clean stuff.
You need some boilerplate files in place for rspec-puppet tests to run. You can either run
Or you can manually setup the files and folders. Here I will describe the minimal set of files you need:
.fixtures.yml is a puppet_spec_helper construct that allows you to symlink in other modules that might be required to test your code. For example you might require functions from the stdlib. How does Rspec know where stdlib is?
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When rspec runs the preparation parts, the spec_helper will create symlinks, or clone repos, or whatever.
spec/spec_helper.rb is a file you need in place for your rspec tests to reference. If you are using the puppetlabs_spec_helper gem, it is only one line:
This spec_helper.rb file can now be referenced, and by doing so will allow Ruby to import all of the puppet-specific Rspec matchers it needs to function.
For example, at the top of every Rspec ruby file you should see something like this:
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Putting files in the right places allows Rspec to autodetect them. Giving them a conventional name allows rspec to glob them.
As the scope of your testing increases, a well-organized directory structure is essential:
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How to write puppet tests is outside the scope of this particular blog post.
I recommend looking at solid examples from puppetlabs’ github, or right from the offical documentation.
But essentially, Rspec runs puppet in a noop mode, only generating a catelog of what it would do. Then the rspec tests use matchers to describe assertions against the catelog.