How do I write a Rails 3.1 engine controller test in rspec?

Question

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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