Capybara::DSL en la librería 
capybara/dsl,
la Session es inicializada automaticamente.
[~/sinatra/sinatra-selenium/intro(master)]$ cat hello_lpp_dsl.rb 
require 'capybara/dsl'
require 'capybara/poltergeist'
include Capybara::DSL
Capybara.default_driver = :poltergeist
visit "http://nereida.deioc.ull.es/~lpp/perlexamples/"
if has_content?("Apuntes de RUBY")
  puts "All shiny, captain!"
else
  puts ":( no tagline found, possibly something's broken"
  exit(-1)
end
Al ejecutar este programa obtenemos un warning:
[~/sinatra/sinatra-selenium/intro(master)]$ ruby hello_lpp_dsl.rb including Capybara::DSL in the global scope is not recommended! All shiny, captain!
Si queremos silenciar este warning podemos usar la opción -W del intérprete Ruby estableciendo el nivel a 0:
[~/sinatra/sinatra-selenium/intro(master)]$ ruby -W0 hello_lpp_dsl.rb All shiny, captain!