使用Mocha模拟/存储应用程序控制器方法（使用Shoulda，Rails 3）

Question

While writing functional tests for a controller, I came across a scenario where I have a before_filter requesting some information from the database that one of my tests requires. I'm using Factory_girl to generate test data but I want to avoid hitting the database when its not explicitly needed. I'd also like to avoid testing my before_filter method here (I plan to test it in a separate test). As I understand, mocking/stubbing is the way to accomplish this.

My question is, what is the best way to mock/stub this method in this scenario.

My before filter method looks for a site in the db based on a subdomain found in the URL and sets an instance variable to be used in the controller:

#application_controller.rb

def load_site_from_subdomain
  @site = Site.first(:conditions => { :subdomain => request.subdomain })
end

My controller that uses this method as a before_filter:

# pages_controller.rb

before_filter :load_site_from_subdomain

def show
  @page = @site.pages.find_by_id_or_slug(params[:id]).first
  respond_to do |format|
    format.html { render_themed_template }
    format.xml  { render :xml => @page }
  end
end

As you can see, it relies on the @site variable to be set (by the before_filter). During testing however, I'd like to have the test assume that @site has been set, and that it has at least 1 associated page (found by @site.pages ). I'd like to then test my load_site_from_subdomain method later.

Here is what I have in my test (using Shoulda & Mocha):

context "a GET request to the #show action" do

  setup do
    @page = Factory(:page)
    @site = Factory.build(:site)

    # stub out the @page.site method so it doesn't go 
    # looking in the db for the site record, this is
    # used in this test to add a subdomain to the URL
    # when requesting the page
    @page.stubs(:site).returns(@site)

    # this is where I think I should stub the load_site_from_subdomain
    # method, so the @site variable will still be set
    # in the controller. I'm just not sure how to do that.
    @controller.stubs(:load_site_from_subdomain).returns(@site)

    @request.host = "#{ @page.site.subdomain }.example.com"
    get :show, :id => @page.id
  end

  should assign_to(:site)
  should assign_to(:page)
  should respond_with(:success)

end

This leaves me with an error in my test results telling me that @site is nil.

I feel like I'm going about this the wrong way. I know it would be easy to simply just Factory.create the site so it exists in the db, but as I said earlier, I'd like to reduce the db usage to help keep my tests speedy.

Answer 1

尝试删除'Site.first'，因为它是你需要存根的@site var的设置，而不是来自before_filter的返回的var。

Answer 2

The reason why your @site is nil because your load_site_from_subdomain does the value assignment for @site -- it does not return any value hence your stubbing for load_site_from_subdomain simply doesn't assign the value to @site . There are two work-arounds for this:

First way:

Change load_site_from_subdomain to just do a return value:

def load_site_from_subdomain
  Site.first(:conditions => { :subdomain => request.subdomain })
end

and then remove the before_filter :load_site_from_subdomain and change your show to:

def show
  @site = load_site_from_subdomain
  @page = @site.pages.find_by_id_or_slug(params[:id]).first
  respond_to do |format|
    format.html { render_themed_template }
    format.xml  { render :xml => @page }
  end
end

And then do the stubbing in the test:

@controller.stubs(:load_site_from_subdomain).returns(@site)

that ensure our @site is stubbed indirectly via load_site_from_subdomain

Second way

To stub the Site.first , I do not really like this approach as in functional test, we do not really care about how the model is retrieved but the behaviour of the respond . Anyway, if you feel like going this path, you could stub it out in your test:

Site.stubs(:first).returns(@site)