Rails::SessionCookie

Fast, loosely coupled requests specs for a cookie-authenticated application.

Why

Probably, you might have seen a lot code like this:

# config/initializers/session_store.rb
Rails.application.config.session_store :cookie_store

# authentificaing method (maybe Devise or whatever)
session[:current_user_id] = current_user.id

# somewhere in helper for request specs
def login(current_user)
  post '/login', auth_data(current_user)
end

# now every request spec is calling login request
RSpec.describe 'User inferface', type: :request do
  let(:user) { create :user }

  before do
    login(user)
  end

  it 'shows private data' do
    get '/dashboard'
  end
end

In a usual user-driven application this tightly couples all request specs, which require authentication, to the login process. If it fails - everything fails. If it's not blazingly fast - it slows the whole suite down.

One may move to token-based authentification, especially when having API. That's reasonable and nice. But we can think about a session cookie as a token passed in a special header!

This gem replaces your usual process with the simplest 2 rails middleware pass. Rails is modular, that's cool :)

Installation

# Gemfile
gem 'rails-session_cookie', group: :test

Usage in requests specs

# spec_helper.rb
require 'rails/session_cookie'

def login(current_user)
  # depending on Rails version and session configuration this looks like "cookie_store_key=data--digest; path=/; HttpOnly"
  raw_session_cookie = Rails::SessionCookie::App.new(current_user_id: current_user.id).session_cookie

  # note, it's raw, not `<<`
  cookies.merge(raw_session_cookie)
end

# ...everything else the same

Now you can cache raw_session_cookie globally or per-thread depending on current_user_id to get things even faster!

You can also use the raw_session_cookie directly like this:

get "/", {}, { "HTTP_COOKIE" => raw_session_cookie }

Strictly speaking, you may cache Set-Cookie response header from /login URL to achieve same speed (but not coupling ;) However, never saw this in practice, and consider caching of requests in before-phase bad. YMMV.

Advanced usage

If you need more sophisticated logic:

  auth_app = proc { |env|
    # do your magic
    env[Rails::SessionCookie::RACK_SESSION].merge!(context)
    [200, {}, []]
  }
  raw_session_cookie = Rails::SessionCookie::App.new(auth_app).session_cookie
end

Of course, you can just make use (and reuse!) of as many procs as you wish.

This effectively achieves the effect as this PR#18230, which allows session mutation in a less invasive way in regard to Rails itself ;)

Warden / Devise

Getting session cookie is dead-simple, just get the cookie this way:

raw_session_cookie = Rails::SessionCookie::WardenApp.new(user).session_cookie

Feature tests using Capybara

Get the cookie as described above according to your setup, and assign this way:

Capybara.current_session.driver.browser.set_cookie raw_session_cookie

TODO: Only tested with :rack_test driver!

Benchmarks

NOTE: Sometimes devise's sing_in is still faster than SessionCookie (a little though), because Warden uses an ugly hack, in my opinion, to support test-mode authentication.

But, still, in average performance of this gem is not worse if used with user_id->cookie caching Besides, authentication becomes as transparent as possible and should increase readability if you understand HTTP session cookies principles.

$ appraisal rails-5.1-warden rspec -t performance spec/benchmarks

Speed using capybara in feature test
  correctness of
    SessionCookie
      is correct
    Devise Helpers
      are correct
  against Devise::Test::Helpers
    is obviously slower separately
    is not slower than devise helpers if using cache and executing multiple specs in a suite

Speed using custom sign-in in request test
  correctness of
    SessionCookie
      is correct
    usual session controller
      is correct
  against custom sign in route
    is faster separately without cache

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7 examples, 0 failures

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/razum2um/rails-session_cookie.