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Testing Mounted Engine Authentication Workflows in Devise

This test suite validates the authentication and routing behavior of a mountable Rails engine integrated with Devise authentication. It ensures proper access control and route handling for both authenticated and unauthenticated users.

Test Coverage Overview

The test suite provides comprehensive coverage of mountable engine authentication scenarios:

Authentication redirect flows
Authenticated access to root routes
Inner route accessibility
Non-existent route handling

Implementation Analysis

The testing approach implements a modular design using Rails Engine isolation and Devise integration testing patterns. It leverages Rails’ route management capabilities with disable_clear_and_finalize for maintaining route consistency during tests.

Key patterns include authenticated mounting, namespace isolation, and controller response validation.

Technical Details

Testing infrastructure includes:

Devise::IntegrationTest framework
Rails Engine configuration
Custom TestsController implementation
Route authentication wrapping
Isolated namespace configuration

Best Practices Demonstrated

The test suite exemplifies several testing best practices:

Comprehensive authentication state testing
Proper route isolation and mounting
Error case handling for invalid routes
Clear test case organization
Effective use of helper methods for authentication

heartcombo/devise

test/integration/mounted_engine_test.rb

            
# frozen_string_literal: true

require 'test_helper'

module MyMountableEngine
  class Engine < ::Rails::Engine
    isolate_namespace MyMountableEngine
  end
  class TestsController < ActionController::Base
    def index
      render plain: 'Root test successful'
    end
    def inner_route
      render plain: 'Inner route test successful'
    end
  end
end

MyMountableEngine::Engine.routes.draw do
  get 'test', to: 'tests#inner_route'
  root to: 'tests#index'
end

# If disable_clear_and_finalize is set to true, Rails will not clear other routes when calling
# again the draw method. Look at the source code at:
# http://www.rubydoc.info/docs/rails/ActionDispatch/Routing/RouteSet:draw
Rails.application.routes.disable_clear_and_finalize = true

Rails.application.routes.draw do
  authenticate(:user) do
    mount MyMountableEngine::Engine, at: '/mountable_engine'
  end
end

class AuthenticatedMountedEngineTest < Devise::IntegrationTest
  test 'redirects to the sign in page when not authenticated' do
    get '/mountable_engine'
    follow_redirect!

    assert_response :ok
    assert_contain 'You need to sign in or sign up before continuing.'
  end

  test 'renders the mounted engine when authenticated' do
    sign_in_as_user
    get '/mountable_engine'

    assert_response :success
    assert_contain 'Root test successful'
  end


  test 'renders a inner route of the mounted engine when authenticated' do
    sign_in_as_user
    get '/mountable_engine/test'

    assert_response :success
    assert_contain 'Inner route test successful'
  end

  test 'respond properly to a non existing route of the mounted engine' do
    sign_in_as_user
    
    assert_raise ActionController::RoutingError do
      get '/mountable_engine/non-existing-route'
    end
  end
end