problem in testing async sinatra app in rails 3

async_test.rb

class AsyncTest < Sinatra::Base
  register Sinatra::Async

  aget '/' do
    body "hello async"
  end
end

async_test_spec.rb

require 'spec_helper'
require 'sinatra/async/test'

describe AsyncTest do
  include Rack::Test::Methods
  include Sinatra::Async::Test::Methods

  def app
    AsyncTest
  end

  describe 'AGET /' do
    it 'should response "hello async"' do
      aget '/'
      last_response.body.should == 'hello async'
    end
  end
end

Gemfile

gem 'thin'
gem 'sinatra', :require => 'sinatra/base'
gem 'async_sinatra', :require => 'sinatra/async'
group :development, :test do
  gem 'rspec-rails'
end

routes.rb

mount AsyncTest => '/'

rspec_result

F

Failures:

  1) AsyncTest AGET / should response "hello async"
     Failure/Error: aget '/'
     ArgumentError:
       wrong number of arguments (0 for 1)
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/sinatra-1.2.0/lib/sinatra/base.rb:1096:in `options'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/async_sinatra-0.5.0/lib/sinatra/async/test.rb:81:in `async_continue'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/async_sinatra-0.5.0/lib/sinatra/async/test.rb:59:in `aget'
     # ./spec/metals/async_test_spec.rb:14:in `block (3 levels) in <top (required)>'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:49:in `instance_eval'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:49:in `block (2 levels) in run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:106:in `with_around_hooks'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:46:in `block in run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:99:in `block in with_pending_capture'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:98:in `catch'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:98:in `with_pending_capture'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example.rb:45:in `run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:262:in `block in run_examples'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:258:in `map'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:258:in `run_examples'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:232:in `run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:233:in `block in run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:233:in `map'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/example_group.rb:233:in `run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/command_line.rb:27:in `block (2 levels) in run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/command_line.rb:27:in `map'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/command_line.rb:27:in `block in run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/reporter.rb:12:in `report'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/command_line.rb:24:in `run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/runner.rb:55:in `run_in_process'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/runner.rb:46:in `run'
     # /home/ayaya/.rvm/gems/ruby-1.9.2-p180/gems/rspec-core-2.5.1/lib/rspec/core/runner.rb:10:in `block in autorun'

Finished in 0.02255 seconds
1 example, 1 failure