Alternative version of test described here http://re-factor.com/blog/2013/09/27/slow-tests-are-the-symptom-not-the-cause/ using domain model rather than "service object"

mailing_list_spec.rb

describe MailingList do
  let(:notifications) { double('notifications') }
  let(:user) { User.new }

  it 'registers a new user' do
    expect(notifications).to receive(:call).with(user, 'list_name')
    
    mailing_list = MailingList.new('list_name', notifications)
    mailing_list.add(user)
    
    expect(user.mailing_list_name).to eq('list_name')
  end
end

hey Brian, I replied to your comment here: http://re-factor.com/blog/2013/09/27/slow-tests-are-the-symptom-not-the-cause/#comment-1076628266 in case you didn't get a notification for it

happy birthday btw!

One suggestion: I'd use a mock user and expect it to receive #add_to_mailing_list (a new method that's not coming from AR). See the tests here: orend/register@e0b9fd9 (from the post: "If we keep using our own methods instead of active record’s we’ve effectively made persistence and object lookup an implementation detail that’s the concern of the model only.")