Ruby on rails 如何为api控制器的索引操作编写rspec

当我运行这个规范时，它总是给零对象，有人能帮我吗

 require 'spec_helper'

   describe Api::SongsController do
    describe "GET index" do
     it "assigns songs json" do
      song = Song.create(:title => "song")
      get :index, :format => :js
      assigns(:songs).should eq([song])
      end
     end        
   end

还有我的控制器代码

     def index
      songs = Song.all
      if !songs.empty?
       respond_with songs
      else
       render :json => {:message => "No songs found."}
      end
     end

---

控制器应具有实例变量。所以改变

 def index
  songs = Song.all
  if !songs.empty?
   respond_with songs
  else
   render :json => {:message => "No songs found."}
  end
 end

到

---

应该这样做：）

您得到的错误是什么？它引用的是哪一行？运行规范后，预期的是has song实例，但GET has nil。因此，基本上它没有通过测试。基本匹配测试。

 def index
  @songs = Song.all
  if !@songs.empty?
   respond_with @songs
  else
   render :json => {:message => "No songs found."}
  end
 end