default_spec for docker builds (this one is ubuntu-specific)

default_spec.rb

require 'spec_helper'

describe "Dockerfile" do
  before(:all) do
    image = Docker::Image.build_from_dir('.') do |v|
      if (log = JSON.parse(v)) && log.has_key?("stream")
        $stdout.puts log["stream"]
      end
    end

    set :os, family: :debian
    set :backend, :docker
    set :docker_image, image.id
  end

  describe file ('/etc/resolv.conf') do
    its(:content) { should match /nameserver/ }
  end
end