has_many_polymorphs and the open-closed principle

I like has_many_polymorphs. I would love it if only it obeyed the open-closed principle.

Let's say I have a PetOwner model, and I want it to have_many pets polymorphically.

has_many_polymorphs lets you do this:

class PetOwner < ActiveRecord::Base
  has_many_polymorphs :from => [:dogs, :cats, :fish]
  ...
end

But what if I later decide I want to add a Ferret class? In addition to

class Ferret < AbstractPet
  ...
end

I also have to change PetOwner:

class PetOwner < ActiveRecord::Base
  has_many_polymorphs :from => [:dogs, :cats, :fish, :ferrets]
  ...
end

It would be really lovely if has_many_polymorphs could just tell what has inherited from AbstractPet. There's no reason you can't do this (in fact, I did before I wrote this post), but there's a timing problem: all of the inherited classes have to load before PetOwner does. The has_many_polymorphs ... call only happens when PetOwner is first included, so all of those other classes have to have already registered themselves with AbstractPet (simply by inheriting from it) by then; unfortunately, there's no good way to guarantee class load order without major hacking at the environment.

Sometimes we just have to put up with not-the-best. Alas.

and the test_spec_on_rails journey continues

Test/Spec has a wonderful - if largely unnoticed - feature: you can specify the superclass of contexts. The default is the ole' Test::Unit::TestCase, but that won't always do.

Let's say, hypothetically, you wanted to write some integration tests for your not-quite-shiny Rails app. You'd use ApplicationController::IntegrationTest, right? That way you can do things like get "/posts/34.html" and it would look up the routings and just do the right thing. Awesome.

Except... things aren't quite so simple when using test/spec. Therefore, I bring you an illustrious, illustrative example:

require File.dirname(__FILE__) + '/../test_helper'

class UserStoriesTest < ActionController::IntegrationTest
 fixtures :people, :openid_authentications, :password_authentications
 context "User Stories", ActionController::IntegrationTest do
   context "a person coming to the site to log in", ActionController::IntegrationTest do
     specify "should see the welcome page" do
       get '/'
       template.should.be 'welcome/index'
       status.should.be 200
     end
     specify "should be able to successfully log in with email and password..." do
       post_via_redirect '/login.html', {:email => 'pete.thomas@xahoo.com', :password => 'test'}
       template.should.be 'people/home'
       status.should.be 200
     end
   end
 end

end

test_spec_on_rails continued...

Yesterday, I was very happy because all my controller tests (using test/spec, of course) were passing individually.

Today I decided to run rake test:functionals just to make sure they played well together. CRASH! BOOM! OTHER LOUD NOISES!

The problem, after two hours of debugging, is that I was creating the same context in different controllers. DocumentationControllerTest had a "A guest" context, and so did "AccountControllerTest" and "WelcomeControllerTest"

Test/spec is perfectly happy to merge these . . . I just didn't realize it merged them. I assumed that it would scope the context to its parent TestClass. No such luck.

The solution is quite easy, and really not all that bad practice anyway: scope your contexts manually. For example:

class WelcomeControllerTest < Test::Unit::TestCase
 context "The Welcome Controller" do
   context "A guest" do
     ...
   end
   context "A logged-in user" do
     ...
   end
 end
end