Question

Probably a simple answer that’s mock or stub related but I’m newish and trying to get a better understanding of things… I’m trying to understand why test resources aren’t actually deleted? but specs pass as if they were? This may (or may not) be unique to RSpec?!?

I have a new project using RSpec and generated a scaffold for a simple Resource

$ rails new destroyer -T
...
$ rails generate rspec:install
...
$ rails g scaffold resource name:string

Everything works, as expected, and specs pass. But I’ve had some curious stuff happen and tests fail in another project so digging deeper I added some logging to my destroy method to see what’s happening:

#app/controllers/resources_controller.rb
def destroy
  @resource = Resource.find(params[:id])
  @resource.destroy
  logger.info "Resource Destroyed: #{@resource.destroyed?}" # <-- added
  logger.info "Persisted after destroy: #{@resource.persisted?}" # <-- added

  respond_to do |format|
    format.html { redirect_to(resources_url) }
    format.xml  { head :ok }
  end
end

When I Destroy a resource I notice this (####) discrepancy in my logs:

development.log:

Started POST "/resources/3" for 127.0.0.1 at 2011-02-16 12:28:25 -0800
  Processing by ResourcesController#destroy as HTML
  Parameters: {"authenticity_token"=>"87+THlPY2Ni7vQCONbeSqwfoeXI2fesc7DIj6EMSaw=", "id"=>"3"}
  Resource Load (0.2ms)  SELECT "resources".* FROM "resources" WHERE "resources"."id" = 3 LIMIT 1
  AREL (0.5ms)  DELETE FROM "resources" WHERE "resources"."id" = 3
Resource Destroyed: true               # <<<<  ###### TRUE ######
Persisted after destroy: false
Redirected to http://localhost:4002/resources
Completed 302 Found in 30ms

and after running the specs I see this in test.log:

  Processing by ResourcesController#destroy as HTML
  Parameters: {"id"=>"1"}
Resource Destroyed: false              # <<<<  ###### FALSE ######
Persisted after destroy: false
Redirected to http://test.host/resources
Completed 302 Found in 4ms

Why are we seeing different states (destroyed?) of a resource depending on the environment we’re running in?

Answer 1

If you are using the generated controller specs, you’ll see something like this for the destroy action:

require 'spec_helper'

describe PostsController do

  def mock_post(stubs={})
    @mock_post ||= mock_model(Post, stubs).as_null_object
  end

  it "destroys the requested post" do
    Post.stub(:find).with("37") { mock_post }
    mock_post.should_receive(:destroy)
    delete :destroy, :id => "37"
  end
end

The spec is not instantiating a real Post object, instead it is using mock_model to create a mock (or ‘test double’). To make it easier to test models, mocks created with mock_model stub out some of the ActiveRecord methods, including destroyed? and persisted?. As a result, these mocks won’t behave exactly the same way as real model instances.