mocha stubs with exception - rspec test not passing

Question

Hey, I am trying to use Mocha and Rspec to test a scenario where a method always raises some exception.

Here is the controller code I am trying to test:

  def add_parent
    begin
      parent = Entity.find_by_id(params[:parent_id])
      if !parent.nil?
        @entity.add_parent!(parent)
        flash[:success] = "Entity successfully updated."
      else
        raise "Parent does not exist."
      end
    rescue
      flash[:error] = "Something bad happened. #{$!}"
    end
    redirect_to @entity
  end

Here is the test code:

it "should flash error if exception is thrown when adding parent" do
      Entity.any_instance.stubs(:add_parent!).raises(Exception)
      lambda do
        post :add_parent, :id => @entity[:id], 
          :parent_id => @parent_entity[:id]
      end.should_not change(@entity.parents, :count)
      flash[:error].should =~ /something bad happened/i
    end

Here is the method which is being stubbed:

  def add_parent!(parent)
    Entity.transaction do
      lock!('lock in share mode')
      self.parents << parent
    end
  end

I am getting the following rspec error, which is pretty uninformative so I don't know how to resolve it..

Failures:

  1) EntitiesController POST 'add_parent' for signed-in users allow access with edit permission should flash error if exception is thrown when adding parent
     Failure/Error: post :add_parent, :id => @entity[:id],
     Exception
     # ./app/controllers/entities_controller.rb:81:in `add_parent'
     # ./spec/controllers/entities_controller_spec.rb:1010

Answer 1

Wooah, first of all, it's a very bad habit to rescue from a big chunk of code without give the exception class you are expecting here. rescueing everything is no good. Best remove the whole rescueing, maybe use find over find_by_id so rails can catch that 404 error and you aren't bothered about. On the other hand, is this error supposed to happen a lot? Looks like some db-stuff going on so I wouldn't expect it to fail.

Secondly, I think you must test like the manual says about raise_error http://relishapp.com/rspec/rspec-expectations/v/2-6/dir/built-in-matchers/raise-error-matcher

Answer 2

rescue with no argument will rescue StandardError and its descendants. If you want to catch ALL exceptions, you should rescue Exception as all exceptions descend from class Exception.

Source: http://www.ruby-forum.com/topic/44495