How to write a Rails 3.1 engine controller test in rspec

routesrspecruby-on-rails-3ruby-on-rails-3.1

I have written a Rails 3.1 engine with the namespace Posts. Hence, my controllers are found in app/controllers/posts/, my models in app/models/posts, etc. I can test the models just fine. The spec for one model looks like…

module Posts
  describe Post do
    describe 'Associations' do
      it ...
      end

… and everything works fine.

However, the specs for the controllers do not work. The Rails engine is mounted at /posts, yet the controller is Posts::PostController. Thus, the tests look for the controller route to be posts/posts. 

  describe "GET index" do
    it "assigns all posts as @posts" do
      Posts::Post.stub(:all) { [mock_post] }
       get :index
       assigns(:posts).should eq([mock_post])
    end
  end

which yields…

  1) Posts::PostsController GET index assigns all posts as @posts
     Failure/Error: get :index
     ActionController::RoutingError:
     No route matches {:controller=>"posts/posts"}
     # ./spec/controllers/posts/posts_controller_spec.rb:16

I've tried all sorts of tricks in the test app's routes file… :namespace, etc, to no avail.

How do I make this work? It seems like it won't, since the engine puts the controller at /posts, yet the namespacing puts the controller at /posts/posts for the purpose of testing.

Best Answer

I'm assuming you're testing your engine with a dummy rails app, like the one that would be generated by enginex.

Your engine should be mounted in the dummy app:

In spec/dummy/config/routes.rb:

Dummy::Application.routes.draw do
  mount Posts::Engine => '/posts-prefix'
end

My second assumption is that your engine is isolated:

In lib/posts.rb:

module Posts
  class Engine < Rails::Engine
    isolate_namespace Posts
  end
end

I don't know if these two assumptions are really required, but that is how my own engine is structured.

The workaround is quite simple, instead of this

get :show, :id => 1

use this

get :show, {:id => 1, :use_route => :posts}

The :posts symbol should be the name of your engine and NOT the path where it is mounted.

This works because the get method parameters are passed straight to ActionDispatch::Routing::RouteSet::Generator#initialize (defined here), which in turn uses @named_route to get the correct route from Rack::Mount::RouteSet#generate (see here and here).

Plunging into the rails internals is fun, but quite time consuming, I would not do this every day ;-) .

HTH

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