Mocking/Stubbing an Application Controller method with Mocha (Using 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

Try stubbing out 'Site.first' since it the the setting of the @site var that you need to stub and not the returned var from the before_filter.

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)