public void When_a_user_signs_up_with_a_referral_from_a_friend()
{
// test as much of the implementation as possible
directory = new CustomerDirectory(new InMemoryDatabase());
var policy = new ReferralPolicy();
// cannot test emailing implementation - easier to stub
emailer = MockRepository.GenerateStub<IEmailer>();
service = new ReferAFriendService(directory, policy, emailer);
service.ReferAFriend(referrerId, friendsDetails);
}