Test case for Ruby on Rails issue #13537 - https://github.com/rails/rails/issues/13537

rails-13537.rb

require 'action_controller/railtie'
require 'minitest/autorun'

class RoutingApp < Rails::Application
  config.eager_load = false
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: 'session'
  config.secret_key_base = 'secret'
end

RoutingApp.initialize!

RoutingApp.routes.draw do
  resources :releases, only: [:index, :show], constraints: { id: /[0-9\.]+/ } do
    resource :image, only: [:download] do
      member do
        get 'download'
      end
    end
  end
end

require 'rails/test_help'

class RoutingTest < ActiveSupport::TestCase
  include Rails.application.routes.url_helpers

  def test_nested_singular_resource_path
    assert_equal '/releases/1.9.0/image/download', download_release_image_path('1.9.0')
  end
end