Killing observers

• decreases startup time by not loading all your models
• makes it possible to preload config/environment.rb and still test models -> spin/zeus
• makes dependencies obvious
• replaces ActiveRecord magic with ruby
• makes your app Rails 4 ready

Before:

# config/environment.rb
config.observers = [:foo_observer] 

# app/observers/foo_observer.rb
class FooObserver < ActiveRecord::Observer
  observes :user

  def after_save(user)
    ....
  end
end

After:

# app/models/user.rb
class User < ActiveRecord::Base
  include FooObserver
end

# app/observers/foo_observer.rb
module FooObserver
  class << self
    def included(base)
      this = self
      base.after_save{|user| this.more_descriptive_name(user) }
    end

    def more_descriptive_name(user)
      ...
    end
  end
end

Normal headers like Accept or :authorization do not work in rails 3 integration tests and you need to convert everything to HTTP_ACCEPT etc, to help find all those places and make sure you do not introduce new bugs in rails 2 add this:

# https://grosser.it/2012/10/19/upgrading-to-rails-3-0-making-sure-you-use-rack-headers-everywhere/
# message can be changed on rails 3, but keep the warning, it's so hard to track down missing headers
# maybe try to remove in rails 3.1+
# can be tested by e.g. changing header to Accept instead of HTTP_ACCEPT
class ActionController::Integration::Session
  # headers that are only used by our code and not rails/rack can be whitelisted, but make sure they work on rails 2 and 3
  HEADER_WHITELIST = ['Funky-Headers-You-Have-To-Use']
  def process_with_header_warning(*args)
    if args[3] && bad = args[3].keys.detect{|k| !k.is_a?(String) || (!HEADER_WHITELIST.include?(k) && k !~ /^[A-Z_\d]+$/) }
      raise "Header #{bad} will not work on rails 3, please uppercase (Content-Type -> CONTENT_TYPE) and prefix HTTP_ (Accept -> HTTP_ACCEPT)"
    end
    process_without_header_warning(*args)
  end
  alias_method_chain :process, :header_warning
end

Integration tests call the whole rack middleware stack, but stubbornly return the last controller response, which can be completely different especially if you use warden or other middleware-tools.

See actionpack-2.3.14/lib/action_controller/integration.rb:342

To fix that and prepare for Rails 3 (which also relies on rack response) do this:

# test/test_helper.rb

if Rails::VERSION::MAJOR == 2
  # https://grosser.it/2012/10/19/rails-2-your-integration-tests-are-lying/
  # make integration tests use rack response, so we can test our middlewares
  # and not only the pure controller response

  ActionController::Base.class_eval do
    # this is usually done just-in-time by #process but we need to do it earlier
    include ActionController::Integration::ControllerCapture

    # then we hide last_instantiation from #process
    def self.last_instantiation;end
  end

  ActionController::Integration::Session.class_eval do
    def process_with_rackify(*args)
      process_without_rackify(*args)
    ensure
      # needed e.g. inside of assert_redirect_to
      capture = ActionController::Integration::ControllerCapture::ClassMethods

      # not set by original #process
      @response.redirected_to = @response.headers["Location"] if @response
      if @controller = capture.send(:class_variable_get, :@@last_instantiation)
        @request = @controller.request
        @response.template = @controller.response.template if @controller.response
        @controller.send(:set_test_assigns)
      end
    end
    alias_method_chain :process, :rackify
  end
end