How can I stub a controller helper method in a view spec with RSpec 3.4?

问题

I'm testing a view with RSpec (3.4 on Rails 4.2.5). And I use the decent_exposure gem in my CRUD controller. decent_exposure makes it easy to define named methods that are made available to my views and which memoize the resultant values.

But I don't understand how I can stub these methods in a view spec. I tried do it according to the RSpec documentation, but it raises an error.

Why doesn't it work? How can I stub the method article in the view?

My controller

class Account::ArticlesController < Account::BaseController
  expose(:articles) { current_user.articles }
  expose(:article, attributes: :article_params)

  # POST /account/articles
  # POST /account/articles.json
  def create
    respond_to do |format|
      if article.save
        format.html { redirect_to account_article_url(article), notice: 'Article was successfully created.' }
        format.json { render :show, status: :created, location: account_article_url(article) }
      else
        format.html { render :new }
        format.json { render json: article.errors, status: :unprocessable_entity }
      end
    end
  end

  # PATCH/PUT /account/articles/1
  # PATCH/PUT /account/articles/1.json
  def update
    respond_to do |format|
      if article.update(article_params)
        format.html { redirect_to account_article_url(article), notice: 'Article was successfully updated.' }
        format.json { render :show, status: :ok, location: account_article_url(article) }
      else
        format.html { render :edit }
        format.json { render json: article.errors, status: :unprocessable_entity }
      end
    end
  end

  # DELETE /account/articles/1
  # DELETE /account/articles/1.json
  def destroy
    respond_to do |format|
      if article.destroy
        format.html { redirect_to account_articles_url, notice: 'Article was successfully destroyed.' }
        format.json { head :no_content }
      else
        format.html { redirect_to account_articles_url, notice: 'Article was not destroyed.' }
        format.json { render json: article.errors, status: :unprocessable_entity }
      end
    end
  end

  private

  def article_params
    params.require(:article).permit(:title, :announce, :content, :is_published, :published_at)
  end

end

And I have a view spec

require 'rails_helper'

RSpec.describe 'account/articles/new', type: :view do

  before do
    allow(view).to receive(:article).and_return(build(:article))
  end

  it 'renders new article form' do
    render
    expect(rendered).to match %Q{form[action=#{account_articles_path}][method=post]}
  end
end

But it raises an error

Failures:

  1) account/articles/new renders new article form
     Failure/Error: allow(view).to receive(:article).and_return(build(:article))
       #<#<Class:0x007fe85c2c7620>:0x007fe85d161208 @_routes=nil, @_config={}, @view_renderer=#<ActionView::Renderer:0x007fe85d1613c0 @lookup_context=#<ActionView::LookupContext:0x007fe85d1615a0 @details_key=nil, @details={:locale=>[:en], :formats=>[:html, :text, :js, :css, :ics, :csv, :vcf, :png, :jpeg, :gif, :bmp, :tiff, :mpeg, :xml, :rss, :atom, :yaml, :multipart_form, :url_encoded_form, :json, :pdf, :zip], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :coffee, :jbuilder, :haml]}, @skip_default_locale=false, @cache=true, @prefixes=["", "account/articles"], @rendered_format=nil, @view_paths=#<ActionView::PathSet:0x007fe85d1614d8 @paths=[#<ActionView::OptimizedFileSystemResolver:0x007fe85d37fb48 @pattern=":prefix/:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}", @cache=#<ActionView::Resolver::Cache:0x007fe85d37fb20 @data=#<ActionView::Resolver::Cache::SmallCache:0x007fe85d37faf8 @backend={}, @default_proc=#<Proc:0x007fe85f071198@/Users/et/.rvm/gems/ruby-2.2.2/gems/actionview-4.2.5/lib/action_view/template/resolver.rb:49 (lambda)>>>, @path="/Users/et/Documents/projects/test-blog/app/views">, #<ActionView::OptimizedFileSystemResolver:0x007fe85d37feb8 @pattern=":prefix/:action{.:locale,}{.:formats,}{+:variants,}{.:handlers,}", @cache=#<ActionView::Resolver::Cache:0x007fe85d37fe90 @data=#<ActionView::Resolver::Cache::SmallCache:0x007fe85d37fe68 @backend={}, @default_proc=#<Proc:0x007fe85f071198@/Users/et/.rvm/gems/ruby-2.2.2/gems/actionview-4.2.5/lib/action_view/template/resolver.rb:49 (lambda)>>>, @path="/Users/et/.rvm/gems/ruby-2.2.2/gems/devise-3.5.3/app/views">]>>>, @request=#<ActionController::TestRequest:0x007fe85c35e048 @env={"rack.version"=>[1, 3], "rack.input"=>#<StringIO:0x007fe85f87eca0>, "rack.errors"=>#<StringIO:0x007fe85f87ed40>, "rack.multithread"=>true, "rack.multiprocess"=>true, "rack.run_once"=>false, "REQUEST_METHOD"=>"GET", "SERVER_NAME"=>"example.org", 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     # ./spec/views/account/articles/new.html.haml_spec.rb:6:in `block (2 levels) in <top (required)>'

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1 example, 1 failure

Failed examples:

rspec ./spec/views/account/articles/new.html.haml_spec.rb:9 # account/articles/new renders new article form

回答1:

require 'rails_helper'

RSpec.describe 'account/articles/new', type: :view do

  it 'renders new article form' do
    stub_article { Article.new }
    render
    expect(rendered).to match(%r{form.+id="new_article".+action=\"#{account_articles_path}".+accept-charset=\"UTF-8\".+method=\"post\"})
  end

  def stub_article(&block)
    controller.singleton_class.class_exec(block) do
      helper_method :article
      define_method :article do
        block.call
      end
    end
  end

end

回答2:

You can't stub article because

• rspec-mocks' verify_partial_doubles configuration parameter is set to true, so RSpec only lets you stub and mock methods that an object implements, and
• your controller doesn't actually implement article, so RSpec doesn't let you stub it.

You have two options:

1. Disable verify_partial_doubles. This is a bad idea, because it will allow you to make mistakes in stubbing and mocking. Nonetheless, here's how to do it if you must: You probably have the following in your spec_helper.rb:

   RSpec.configure do |config|
     config.mock_with :rspec do |mocks|
       mocks.verify_partial_doubles = true
     end
   end
   

   Change it to verify_partial_doubles = false.

2. Add the following manual 'stub' to your example:

   def view.article
     build(:article)
   end
   

   Or, if the view calls article more than once, build the article outside the method or just return it from the method.

There is a discussion of this situation in an rspec-rails Github issue.

来源：https://stackoverflow.com/questions/35240236/how-can-i-stub-a-controller-helper-method-in-a-view-spec-with-rspec-3-4