latest_version_in_artifactory.rb

require 'artifactory'
require 'semantic'

RSpec::Matchers.define :be_latest_version_in_artifactory do
  # If I define this method outside of this block then it is (unintuitively) not in scope within the block due
  # to dynamic class voodoo. If I define it outside of the block, it is also unavailable to the outside world,
  # so I can't call it in any control blocks.
  def normalize_version_to_semver(version)
    version.gsub(/~/, '-')
  end

  match do |package|
    package_info = package.info
    @actual_version = Semantic::Version.new(normalize_version_to_semver(package_info[:version]))
    @expected_version = Artifactory::Resource::Artifact.search(options.merge(name: "#{package_info[:name]}*.deb"))
            .map(&:properties)
            .map { |p| p['deb.version'] }
            .flatten
            .map { |v| Semantic::Version.new(normalize_version_to_semver(v)) }
            .max
    @actual_version == @expected_version
  end

  chain :with_options do |options|
    @options = options
  end

  description do
    res = 'be the latest version'
    res += " (expected '#{@expected_version}', found '#{@actual_version}')" unless @expected_version.nil?
    res += " with options #{@options}" unless @options.nil?
    res
  end

  def options
    @options || {}
  end
end

service_spec.rb

artifactory_endpoint = attribute('artifactory_endpoint', 
                                 default: 'https://artifactory.example.com/artifactory',
                                 description: 'The base url to the Artifactory instance that packages will be installed from')
artifactory_username = attribute('artifactory_username', description: 'The user to log in to artifactory as')
artifactory_password = attribute('artifactory_key', description: 'The API key to log in to artifactory with')
backend_version = attribute('backend_version', 
                             description: 'A backend version to install; by default the latest version available')

# This is another thing I'd prefer to do in something like a spec_helper, since it noises up what I'm actually testing here,
# but apparently inspec attributes are only available in spec files
Artifactory.configure do |c|
  c.endpoint = artifactory_endpoint
  c.username = artifactory_username
  c.password = artifactory_password
end

control 'backend-002' do
  impact 1.0
  title 'Backend installation'
  desc 'The backend service should be installed'

  describe.one do
    describe package('backend') do
      it "By default, installs the latest version" do
        expect(u2you_backend_version).to be_nil
      end

      it { is_expected.to be_installed }
      # custom matcher works fine here, since it just queries the package that's
      # passed to it.
      it { is_expected.to be_latest_version_in_artifactory }
    end

    describe package('backend') do
      # Since I can't declare this in global scope in libraries, I have to redefine it here. Note that this is the
      # broadest scope I could get it to work in. Putting it in the describe.one block hid it, as did putting it in
      # the control block, and in (what one would expect to be) global scope.
      def normalize_version_to_semver(version)
        version.gsub(/~/, '-')
      end

      it "If a version is specified, installs that version" do
        expect(backend_version).to_not be_nil
      end

      it { is_expected.to be_installed }
      it { expect(normalize_version_to_semver(subject.version)).to eq backend_version }
    end
  end
end