spec_helper.rb

 require 'serverspec'
 require 'pathname'
 require 'net/ssh'

 include Serverspec::Helper::Ssh
 include Serverspec::Helper::DetectOS

 RSpec.configure do |c|
   if ENV['ASK_SUDO_PASSWORD']
     require 'highline/import'
     c.sudo_password = ask("Enter sudo password: ") { |q| q.echo = false }
   else
     c.sudo_password = ENV['SUDO_PASSWORD']
   end
   c.before :all do
     block = self.class.metadata[:example_group_block]
     if RUBY_VERSION.start_with?('1.8')
       file = block.to_s.match(/.*@(.*):[0-9]+>/)[1]
     else
       file = block.source_location.first
     end
     host  = File.basename(Pathname.new(file).dirname)

     if c.host != host
       c.ssh.close if c.ssh
       c.host  = host
       options = Net::SSH::Config.for(c.host)
       user    = options[:user] || Etc.getlogin

       config = `vagrant ssh-config --host #{host}`
       if config != ''
         config.each_line do |line|
           if match = /HostName (.*)/.match(line)
             c.host = match[1]
           elsif  match = /User (.*)/.match(line)
             user = match[1]
           elsif match = /IdentityFile (.*)/.match(line)
             options[:keys] =  [match[1].gsub(/"/,'')]
           elsif match = /Port (.*)/.match(line)
             options[:port] = match[1]
           end
         end
       end

      c.ssh   = Net::SSH.start(c.host, user, options)
      c.os    = backend(Serverspec::Commands::Base).check_os
     end
   end
end