Spork & Rails 3.1 engine: helpers are not reloaded - ruby-on-rails

Question

I'm developing a Rails 3.1 engine and want to test it. I use RSpec for this, and everything works nicely, but when trying to use Spork, I have the problem that my helpers are not correctly reloaded.
I read a lot about a similar problem with models, and I came up with the following possible fix:
# my_engine/spec/spec_helper.rb
ActiveSupport::Dependencies.clear
ActiveRecord::Base.instantiate_observers
Dir[File.join(File.dirname(__FILE__), '..', 'app', 'helpers', '*.rb')].each do |file|
require file
end
# my_engine/spec/dummy/config/environments/test.rb
Dummy::Application.configure do
# ...
config.cache_classes = !(ENV['DRB'] == 'true') # Ensure that classes aren't cached when using Spork.
# ...
end
This works as far as it definitely is reloading ever helper file (I added a breakpoint to check this), but the changes are not reflected within the tests, only a restart of Spork does. Maybe it's because helpers are modules, and the tests don't rely on the module but on the classes that implement the modules, so the modules are properly reloaded but not properly mixed in??
At the time being, I'm just putting all intitializer code into the each_run block:
# Configure Rails Environment
ENV["RAILS_ENV"] = "test"
require File.expand_path("../dummy/config/environment.rb", __FILE__)
require 'rspec/rails'
Rails.backtrace_cleaner.remove_silencers!
# Load support files
Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each { |f| require f }
RSpec.configure do |config|
config.use_transactional_fixtures = true
config.treat_symbols_as_metadata_keys_with_true_values = true
config.filter_run :focus => true
config.run_all_when_everything_filtered = true
end

Answer 1

I have done a lot of research about this topic, and I've written about in these two blog posts:
How to Develop Rails 3.1 Engines with Ease: Part I – The engine
How to Develop Rails 3.1 Engines with Ease: Part II – The gem
Regarding especially to my question above: I can imagine that it didn't work because I didn't require 'rspec/autorun' in the Spork.prefork block, but I'm not completely sure.
Here's the spec_helper.rb for my current engine (which successfully reloads everything as needed):
require 'rubygems'
require 'spork'
Spork.prefork do
ENV["RAILS_ENV"] ||= 'test'
require File.expand_path("../dummy/config/environment", __FILE__)
require 'rspec/rails'
require 'rspec/autorun'
Dir[Rails.root.join("spec/support/**/*.rb")].each {|f| require f}
RSpec.configure do |config|
config.use_transactional_fixtures = true
config.fixture_path = "#{::Rails.root}/spec/fixtures"
config.infer_base_class_for_anonymous_controllers = false
config.treat_symbols_as_metadata_keys_with_true_values = true
config.filter_run :focus => true
config.run_all_when_everything_filtered = true
end
end
Spork.each_run do
# This code will be run each time you run your specs.
end