ActionDispatch::IntegrationTest showing that sessions, cookies and flash all work

integration_test.rb

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

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

TestApp.initialize!

TestApp.routes.draw do
  resources :cookies
  resources :flashes
  resources :sessions
end

class SessionsController < ActionController::Base
  def show
    render text: session[key]
  end

  def update
    session[key] = params[key]
    head :ok
  end

  def destroy
    session.delete(key)
    head :ok
  end

  protected

  def key
    params[:id]
  end
end

class CookiesController < ActionController::Base
  def show
    render text: cookies[key]
  end

  def update
    cookies[key] = params[key]
    head :ok
  end

  def destroy
    cookies.delete(key)
    head :ok
  end

  protected

  def key
    params[:id]
  end
end

class FlashesController < ActionController::Base
  def show
    render text: flash[key]
  end

  def update
    flash[key] = params[key]
    head :ok
  end

  protected

  def key
    params[:id]
  end
end

class SessionTest < ActionDispatch::IntegrationTest
  def test_session_variables_are_persisted
    put '/sessions/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/sessions/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body
  end

  def test_session_variables_are_deleted
    put '/sessions/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/sessions/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body

    delete '/sessions/foo'
    assert_equal 200, response.status

    get '/sessions/foo'
    assert_equal 200, response.status
    assert_equal " ", response.body
  end
end

class CookiesTest < ActionDispatch::IntegrationTest
  def test_cookies_variables_are_persisted
    put '/cookies/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/cookies/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body
  end

  def test_cookies_variables_are_deleted
    put '/cookies/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/cookies/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body

    delete '/cookies/foo'
    assert_equal 200, response.status

    get '/cookies/foo'
    assert_equal 200, response.status
    assert_equal " ", response.body
  end
end

class FlashTest < ActionDispatch::IntegrationTest
  def test_flashes_are_persisted
    put '/flashes/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/flashes/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body
  end

  def test_flashes_are_swept
    put '/flashes/foo', foo: 'bar'
    assert_equal 200, response.status

    get '/flashes/foo'
    assert_equal 200, response.status
    assert_equal "bar", response.body

    get '/flashes/foo'
    assert_equal 200, response.status
    assert_equal " ", response.body
  end
end