Ruby on rails ActionController:：UnknownFormat:带有rspec和get请求（Rails5）

我试图在rails 5上使用rspec进行控制器测试，但在运行测试时，我总是会遇到“ActionController:：UnknownFormat”异常

以下是错误消息：

 Failure/Error: get :index

 ActionController::UnknownFormat:
   MessagesController#index is missing a template for this request format and variant.

   request.formats: ["text/html"]
   request.variant: []

 NOTE! For XHR/Ajax or API requests, this action would normally respond with 204 No Content: an empty white screen. Since you're loading it in a web browser, we assume that you expected to actually render a template, not nothing, so we're showing an error to be extra-clear. If you expect 204 No Content, carry on. That's what you'll get from an XHR or API request. Give it a shot.

以下是rspec代码：

require 'rails_helper'
describe MessagesController do
  describe 'GET #index' do
    it "renders the :index template" do
      get :index
      expect(response).to render_template :index
    end
  end
end

以下是控制器代码：

class MessagesController < ApplicationController
  def index
  end

我在views/messages/index.html.haml中创建了视图文件。 通常，我可以使用本地环境在web浏览器上查看视图文件。 但是，在rspec上，它找不到视图文件。我不明白

知道哪里出了问题吗？

---

我有麻烦了。请帮我看看响应对象，它可能会解释发生了什么。请在问题中添加该问题的打印内容。您是否已将

gem'rails controller testing'

添加到您的gem文件中？请查看响应对象，它可能会解释发生了什么。请在问题中添加该问题的打印件。您是否已将

gem'rails controller testing'

添加到您的gem文件中？

Rails.application.routes.draw do
  resources :messages, only: [:index]
end