Simple test with a capybara server.

capy-test.rb

require 'open-uri'
require 'capybara/rspec'

app = lambda do |env|
  [200, {'Content-Type' => 'text/plain'}, ['Hello rat!']]
end

Capybara.app = app

server = Capybara::Server.new(Capybara.app).boot
url = "http://#{server.host}:#{server.port}"

puts "Server started. (#{url})"

describe "test local server" do
  it "returns 'Hello rat!'" do
    open(url).read.should =~ %r{Hello rat!}
  end
end

Execute with 'rspec capy-test.rb'