Manually set Rails 4 session cookie for tests

gistfile1.rb

#
# Manually set the contents of an encrypted session cookie
#
# Uses the same encryption keys as the Rails app using devise
#
# Based off http://big-elephants.com/2014-01/handling-rails-4-sessions-with-go/
# Verified against https://github.com/rails/rails/blob/master/actionpack/lib/action_dispatch/middleware/cookies.rb
#
class TestSession

  def create_session_cookie(user_id:, csrf_token: nil, flash: {}, session_id: nil, last_request_at: nil)
    hash = {
      session_id: (session_id || "73b9eb8e8f265c5672ed2135a2d518f7"),
      flashes: flash,
      "warden.user.user.key" => [[user_id],"$2a$10$dIKBfN/6tcQsjDAAubmNDu"],
      "warden.user.user.session" => {"last_request_at": (last_request_at || Time.current).to_i},
      _csrf_token: (csrf_token || "n01FGBu5O2RGf7MaB3L0DrcmeMySJhqIP/Q7dDV37Vg=")
    }

    encrypt_session_cookie hash
  end

  def encrypt_session_cookie(hash)
    encryptor.encrypt_and_sign ActiveSupport::JSON.encode hash
  end

  def decrypt_session_cookie(cookie)
    ActiveSupport::JSON.decode encryptor.decrypt_and_verify CGI.unescape cookie
  end

  private

  def config
    Rails.application.config
  end

  def encrypted_cookie_salt
    config.action_dispatch.encrypted_cookie_salt
  end

  def encrypted_signed_cookie_salt
    config.action_dispatch.encrypted_signed_cookie_salt
  end

  def key_generator
    @key_generator ||= ActiveSupport::KeyGenerator.new(Rails.application.secrets.secret_key_base, iterations: 1000)
  end

  def secret
    key_generator.generate_key(encrypted_cookie_salt)
  end

  def sign_secret
    key_generator.generate_key(encrypted_signed_cookie_salt)
  end

  def encryptor
    @encryptor ||= ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: ActiveSupport::MessageEncryptor::NullSerializer)
  end
end