[rspec-users] New rescue_from handling in rspec-rails 1.1.12

[Chris Kampmeier]

Howdy,

This change to rspec-rails in 1.1.12 tripped me up:
http://github.com/dchelimsky/rspec-rails/commit/ef6d2fc15a
(or, see the relevant Lighthouse ticket, here:
http://rspec.lighthouseapp.com/projects/5645/tickets/85)

Basically, we were depending on that "bug" in 1.1.11, since it seemed to
make sense to us. Here's some sample code... I tried to simplify it as much
as possible:

(Or, here's a syntax-highlighted pastie: http://pastie.org/361114)


# spec/controllers/application.rb
class AccessDeniedError < StandardError; end
class ApplicationController < ActionController::Base
  rescue_from AccessDeniedError, :with => :handle_access_denied

  protected

  def handle_access_denied(exception)
    redirect_to "/"
  end
end


# app/controllers/posts_controller.rb
class PostsController < ApplicationController
  def destroy
    @post = Post.find(params[:id])
    raise AccessDeniedError unless @post.destroyable_by?(current_user)

    @post.destroy
    redirect_to posts_url
  end
end


# spec/controllers/posts_controller_spec.rb
describe PostsController do
  describe "handling DELETE /posts/2" do
    it "raises AccessDeniedError if the post isn't destroyable by the
current user" do
      user = mock_model(User)
      post = mock_model(Post, :destroyable_by? => false)

      controller.stub!(:current_user).and_return(user)
      Post.stub!(:find).and_return(post)

      post.should_not_receive(:destroy)
      lambda { delete :destroy, :id => '2' }.should
raise_error(AccessDeniedError)
    end
  end
end


# spec/controllers/appcliation_controller_spec.rb
class ApplicationTestController < ApplicationController
  def access_denied_action
    raise AccessDeniedError
  end
end

describe ApplicationTestController, "#handle_not_found" do
  before do
    controller.use_rails_error_handling!
  end

  it "redirects to the front page" do
    get :access_denied_action
    response.should redirect_to("/")
  end
end


So we'd check that the controller action raises a given error, even thought
it might be rescued somewhere else (not using
controller.use_rails_error_handling!). And then in a different file, we'd
specifically check the ApplicationController to make sure that it rescued
properly (*with* controller.use_rails_error_handling!). We figured that it's
not PostsController's responsibility to do the rescue, so it shouldn't be
tested there.

This also kept our tests DRY; if we changed the rescue behavior, we wouldn't
need to go through all our controller examples and e.g. change the redirect.
It also felt nice and "unit test"-like to me, in that the implementation of
PostsController clearly raises AccessDeniedError, and we'd check for that in
the spec. This impedence mismatch bothers me:

implementation: raise AccessDeniedError
specification: response.should redirect_to("/")

I'm guessing that the argument _for_ the new behavior (in which rescue_from
is always used) is that my PostsController inherits from
ApplicationController, and therefore, inherits its behavior. So when I'm
testing the behavior, it would violate the POLS if the inherited behavior
was somehow missing. For example, I'd sure be confused if a Rails model was
missing a feature of ActiveRecord::Base when used under test.

Anyway, what should I really be doing here? I could use shared examples to
maintain DRY (it_should_behave_like :access_denied); or I could just repeat
myself, because that's the behavior I'm expecting: response.should
redirect_to("/"). Or, I could alias_method_chain
ActionController::Rescue#rescue_action and hack the old behavior back in. I
don't really want to do that, though--somebody who was familiar with RSpec
but hadn't seen our code before would be mighty confused.

Thanks for reading! That was a lot.

Chris Kampmeier
http://shiftcommathree.com
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