I have defined a custom route in 
routes.rb

```
get "packages/city/:location_id",  to: "packages#index"

```

In `controller_spec.rb`, 

```
get :index

```

gives this error,

```
ActionController::UrlGenerationError:
   No route matches {:action=>"index", :controller=>"packages"}

```

How to explicitly specify the custom routes in controller specs?