rspec's should_receive on a non-mock object?

Is it possible to call should_receive on a non-mock object?

If it is, I'm wondering why this test doesn't pass. SiteStyle has_many images and when I call duplicate! on a site_style, I want the images to call duplicate on themselves as well. The test fails. The actual images get duplicated though. Why is that?

SiteStyle model:

class SiteStyle < ActiveRecord::Base
  belongs_to :site
  belongs_to :user
  validates_presence_of :name, :user
  has_many :images, :as => :imageable, :order => "position", :dependent => :destroy

  ...

 开发者_如何学C def duplicate!(user, *args)
    options = args.extract_options!
    to_site ||= Site.find(options[:site_id])
    dup_style = self.class.create :site_id => to_site.id, :name => name, :user_id => user.id
    self.images.each { |image| image.duplicate!(dup_style) }
    dup_style
  end

  ...
end

SiteStyleSpec:

require 'spec_helper'

describe SiteStyle do
  ...

  describe "duplicate!(user, *args)" do
    before do
      @creator = User.make
      @site = Site.make
      @style = SiteStyle.make :site => @site, :user => @creator
    end

    ...

    it "should have a duplicate of the images" do
      @image = Image.make :imageable_type => @style.class.name, :imageable_id => @style.id
      @image.should_receive(:duplicate!).once
      @dup_style = @style.duplicate!(@creator)
    end
  end
end

Error:

Failures:
  ...

  2) SiteStyle duplicate!(user, *args) should have a duplicate of the images
     Failure/Error: @image.should_receive(:duplicate!).once
     (#<Image:0xc7b40d8>).duplicate!(any args)
         expected: 1 time
         received: 0 times
     # ./spec/models/site_style_spec.rb:83

---

Your line here:

@image.should_receive(:duplicate!).once

Is working with only that specific @image instance, and calling should_receive only on it so that expectation doesn't transfer over to the image objects used inside the duplicate method (or any other place where an image is instantiated) even if it is the same record from the database.