cookies_test.rb

begin
  require "bundler/inline"
rescue LoadError => e
  $stderr.puts "Bundler version 1.10 or later is required. Please update your Bundler"
  raise e
end

gemfile(true) do
  source "https://rubygems.org"
  gem "rails", github: "rails/rails", branch: "5-0-stable"
  gem "pry-byebug"
end

require "action_controller/railtie"

class TestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: "cookie_store_key"
  secrets.secret_token    = "secret_token"
  secrets.secret_key_base = "secret_key_base"

  config.logger = Logger.new($stdout)
  Rails.logger  = config.logger

  routes.draw do
    resources :users, only: [:index]
  end
end

class UsersController < ActionController::Base
  def index
    unless cookies[:name].present?
      cookies[:name] = "Alice"
    end
    render plain: "Home"
  end
end

require "minitest/autorun"
require "rack/test"

class UsersControllerTest < ActionController::TestCase
  setup do
    @controller = UsersController.new
    @routes = Rails.application.routes
  end

  test '#index sets a cookie if it is not already present' do
    get :index
    assert_response :ok
    assert_equal "Alice", cookies[:name]

    cookies[:name] = "Bob"

    get :index
    assert_response :ok
    assert_equal "Bob", cookies[:name]
  end
end

output.txt

Fetching git://github.com/rails/rails.git
Fetching gem metadata from https://rubygems.org/........
Fetching version metadata from https://rubygems.org/.
Resolving dependencies...
Using rake 12.0.0
Using concurrent-ruby 1.0.4
Using i18n 0.7.0
Using minitest 5.10.1
Using thread_safe 0.3.5
Using builder 3.2.2
Using erubis 2.7.0
Using mini_portile2 2.1.0
Using rack 2.0.1
Using nio4r 2.0.0
Using websocket-extensions 0.1.2
Using mime-types-data 3.2016.0521
Using arel 7.1.4
Using bundler 1.13.6
Using byebug 9.0.6
Using coderay 1.1.1
Using method_source 0.8.2
Using slop 3.6.0
Using thor 0.19.4
Using tzinfo 1.2.2
Using nokogiri 1.7.0.1
Using rack-test 0.6.3
Using sprockets 3.7.1
Using websocket-driver 0.6.4
Using mime-types 3.1
Using pry 0.10.4
Using activesupport 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using loofah 2.0.3
Using mail 2.6.4
Using pry-byebug 3.4.2
Using rails-dom-testing 2.0.2
Using globalid 0.3.7
Using activemodel 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using rails-html-sanitizer 1.0.3
Using activejob 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using activerecord 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using actionview 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using actionpack 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using actioncable 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using actionmailer 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using railties 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Using sprockets-rails 3.2.0
Using rails 5.0.1 from git://github.com/rails/rails.git (at 5-0-stable@d5e3fd7)
Run options: --seed 56214

# Running:

I, [2017-01-09T18:32:00.743065 #86520]  INFO -- : ---------------------------------------------------------------------------
I, [2017-01-09T18:32:00.743127 #86520]  INFO -- : UsersControllerTest: test_#index_sets_a_cookie_if_it_is_not_already_present
I, [2017-01-09T18:32:00.743139 #86520]  INFO -- : ---------------------------------------------------------------------------
F

Finished in 0.112710s, 8.8723 runs/s, 35.4893 assertions/s.

  1) Failure:
UsersControllerTest#test_#index_sets_a_cookie_if_it_is_not_already_present [test.rb:57]:
Expected: "Bob"
  Actual: "Alice"

1 runs, 4 assertions, 1 failures, 0 errors, 0 skips