Debugging Rspec Of Catalog Application

Running catalogs from RSpec tests is tricky. There are some examples in the existing test base that help doing it. One basic pattern goes like this:

describe SomeThing
  let(:catalog) { Puppet::Resource::Catalog.new }
  context "when doing something else" do
    let(:resource) do
      Puppet::Type::MyType.new(
        :ensure => :present,
	:param  => 'value',
      )
    end

    it "behaves a certain way" do
      catalog.add_resource(resource)
      catalog.apply
      expect( check_result() ).to be_truthy
    end
  end
end

Of course, such tests can fail for various reasons. The test environment can be incredibly fragile at times. But since all the interesting things happen in the catalog.apply method, it’s difficult to probe into it without resorting to pry and friends.

Fortunately, Puppet’s RSpec suite is set up to collect all log output in the special member variable @logs. The easiest way (that I know of) to examine this data in a failing test is temporarily raising it as an exception.

it "behaves a certain way" do
  catalog.add_resource(resource)
  catalog.apply
  raise "#{logs * "\n"}"
  expect( check_result() ).to be_truthy
end

When this test is run, it will fail due to the unexpected exception, dumping the exception details on the terminal. These details consist of the Puppet output as produced when applying the catalog. It closely resembles the output of puppet agent or puppet apply. A very good first step for debugging this kind of test.