RSpec: Expectation on model's not working while testing controller - ruby-on-rails

Question

I'm trying to write a functional test. My test looks as following:
describe PostsController do
it "should create a Post" do
Post.should_receive(:new).once
post :create, { :post => { :caption => "ThePost", :category => "MyCategory" } }
end
end
My PostsController (a part of it actually) looks as following:
PostController < ActiveRecord::Base
def create
#post = Post.new(params[:post])
end
end
Running the test I'm always receiving a failure, which says that the Post class expected :new but never got it. Still, the actual post is created.
I'm a newbie to RSpec. Am I missing something?

Answer 1

EDIT - Threw away the previous rubbish
This should do what you want
require File.dirname(__FILE__) + '/../spec_helper'
describe PostsController do
it "should create a Post" do
attributes = {"Category" => "MyCategory", "caption" => "ThePost"}
Post.stub!(:new).and_return(#post = mock_model(Post, :save => false))
Post.should_receive(:new).with( attributes ).and_return #post
post :create, { :post => attributes }
end
end
This assumes you are using rspecs own mocking library and that you have the rspec_rails gem installed.

Answer 2

You can use the controller method of Rspec-rails to test message expectations on controllers, as described here. So one way of testing your create action is like so:
describe PostsController do
it "should create a Post" do
controller.should_receive(:create).once
post :create, { :post => { :caption => "ThePost", :category => "MyCategory" } }
end
end
EDIT (making an argument)
You might want to consider whether it's a good idea to write a test that depends on the implementation of the create action. If you're testing for anything other than the proper responsibilities of a controller, you run the risk of breaking tests when refactoring, and having to go back and rewrites tests when the implementation changes.
The job of the create action is to create something -- so test for that:
Post.count.should == 1
and then you know whether a Post was created, without depending on how it was created.
EDIT #2 (um...)
I see from your original question that you already know the Post is being created. I'd still argue that you should test for behavior, not implementation, and that checking for whether the model receives a message is not a good thing in a controller test. Maybe what you're doing is debugging, not testing?