Rails rspec No response yet. Request a page first - ruby-on-rails

Question

I'm running a rspec, the script is like this:
require 'spec_helper'
describe Stb do
let(:app) { Stb.new }
before do
#stb = FactoryGirl.create(:stb)
end
subject { #stb }
describe ".login" do
it "ok" do
RestClient.get "http://www.example.com"
last_response.should be_ok
end
end
end
But it turns out:
1) Stb.login ok
Failure/Error: last_response.should ok
Rack::Test::Error:
No response yet. Request a page first.
When I run RestClient.get "http://www.example.com" in the irb, it can return some valid things.
Could someone help me what's wrong with it, or is there something special about last_response
My *spec_helper.rb* is:
# This file is copied to spec/ when you run 'rails generate rspec:install'
ENV["RAILS_ENV"] ||= 'test'
require File.expand_path("../../config/environment", __FILE__)
require 'rspec'
require 'rspec/rails'
require 'rspec/autorun'
require 'rack/test'
require 'em-rspec'
# Requires supporting ruby files with custom matchers and macros, etc,
# in spec/support/ and its subdirectories.
Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}
RSpec.configure do |config|
# ## Mock Framework
#
# If you prefer to use mocha, flexmock or RR, uncomment the appropriate line:
#
# config.mock_with :mocha
# config.mock_with :flexmock
# config.mock_with :rr
config.mock_with :rspec
# Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
config.fixture_path = "#{::Rails.root}/spec/fixtures"
#config.before(:each, type: :controller) { #routes = Api::Engine.routes }
# config.before(:each, type: :routing) { #routes = Api::V4::Server.routes }
#config.fixture_path = "#{::Rails.root}/spec/fixtures"
#config.before(:each, type: :controller) { #routes = Api::Engine.routes }
config.before(:each, type: :routing) { #routes = Api::Engine.routes }
# make rspec stop operation immediately after failed
config.fail_fast = true
# If you're not using ActiveRecord, or you'd prefer not to run each of your
# examples within a transaction, remove the following line or assign false
# instead of true.
config.use_transactional_fixtures = true
# If true, the base class of anonymous controllers will be inferred
# automatically. This will be the default behavior in future versions of
# rspec-rails.
config.infer_base_class_for_anonymous_controllers = false
config.include Rack::Test::Methods
end