[rspec-users] Problem with before filters

David Chelimsky dchelimsky at gmail.com
Mon Nov 2 09:19:11 EST 2009


On Nov 2, 2009, at 3:35 AM, Amit Kulkarni wrote:

> Following is the scenario.
>
> describe BbPostsController, "POST Create" do
>  context "Admin" do
>    fixtures :users, :bb_posts, :user_channels, :channels,
> :channel_features
>      it "should save post" do
>        login_as(:amit)
>        # Added to pass before filters in controller
>        controller.stub!(:validate_channel).and_return(true)
>        controller.stub!(:is_feature_active).and_return(Blog)
>        controller.stub!(:load_categories).and_return(1)
>        @post = mock_model( BbPost, :body => "test_description", :title
> => "test123", :abstract => "test_abstract", :channel_feature_id =>  
> "v1",
> :published => "1", :bb_post_category_id => "1" )
>        BbPost.stub!(:new).and_return @post
>        @post.should_receive( :save )
>        post :create, {:bb_post => {:title => 'test123'}}
>        response.should redirect_to( blog_bb_posts_url(:channel =>
> @channel.brand_name) )
>      end
>
> Following is the controller code:
> class BbPostsController < ApplicationController
>  before_filter :login_required
>  before_filter :validate_channel
>  before_filter :manager_access_required
>  before_filter :is_feature_active
>  before_filter :load_categories, :only => [ :new, :edit, :create,
> :update ]
>
>  # BEFORE FILTER : Feature must active
>  def is_feature_active
>    @feature = @channel.channel_features.by_name( BLOG ).active.first
>    unless @feature
>       flash[ :notice ] = 'Blog feature was not active.'
>       redirect_to requests_features_path
>    end
>  end
>
>  # BEFORE FILTER : Load blog categories
>  def load_categories
>    # manager blog will not have admin specific categories
>    @categories = ( params[ :channel ].camelize == ADMIN_CHANNEL ) ?
> BbPostCategory.visible : BbPostCategory.visible.without_admin
>  end
>
> def create
>    params[ :bb_post ][ :brand_list ] = ADMIN_CHANNEL if params[
> :bb_post ][ :brand_list ].blank?
>    p params
>    @bb_post = @feature.posts.new( params[ :bb_post ] )
>    @bb_post.user = current_user
>    # CREATE Channel Blog post
>    respond_to do |format|
>      if @bb_post.save
>        flash[ :notice ] = 'Blog post was successfully created.'
>        format.html { redirect_to( blog_bb_posts_url ) }
>        format.xml { render :xml => @bb_post, :status => :created,
> :location => @bb_post }
>      else
> load_featured_posts if @bb_post.editorial?
>        format.html { render :action => "new" }
>        format.xml { render :xml => @bb_post.errors, :status =>
> :unprocessable_entity }
>      end
>    end
>  end
>
> Now if i run my specs,i get an error which says
>
> NoMethodError in 'BbPostsController POST Crete dmin should sve post'
> You hve nil object when you didn't expect it!
> The error occurred while evluting nil.posts
> Error comes at "@bb_post = @feature.posts.new( params[ :bb_post ] )"

This tells you that @feature is nil. This is because filter that  
declares @feature and assigns it a value is being stubbed. Although  
very common, using filters to set instance variables makes it  
difficult to test in isolation.

I recommend pushing the model concerns to the model, and use filters  
for application flow control concerns (like authentication/ 
authorization) in the controller. In this case, that would mean  
eliminating the validate_channel, is_feature_active, and  
load_categories filters and simply passing the params to the model.  
I'm not sure of the models and relationships, but I'm imagining  
something like:

def create
   @bb_post = BbPost.new( params[ :bb_post ].merge(:user =>  
current_user) )
   respond_to do |format|
     if @bb_post.save
       ...

All of the logic in the filters and before the assignment of @bb_post  
can be managed in the BbPost model, where it is far easier to spec in  
my experience.

If you don't want to follow that recommendation, you'll have to either  
set up all the state you need in the database for each example, or do  
more invasive setup like this:

   controller.instance_eval { @feature = mock('feature') }

> Just above that line i tried to print params and i get following  
> values:
> #<BbPost:0x44d1cd8 @nme="BbPost_1001">
> {"ction"=>"crete", "controller"=>"bb_posts",
> "bb_post"=>{"brnd_list"=>"BrndPotio
> n", "title"=>"test123"}}
>
> Can somebody help me with this
> Also by using controller.stub!(:validate_channel).and_return(true) can
> somebody tell me actually,what exactly happens here.How does it handle
> before filters.

Filters are just methods that get called implicitly by the controller.  
RSpec's mocking framework doesn't handle them in any special way (nor  
does any test double frameowrk that I'm aware of). Stubs return  
values. They do not set state on the object in question, which is why  
if you stub is_feature_active, for example, that needs to be coupled  
with code that sets the value of @feature on the controller (per above).

HTH,
David


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