factories.rb

# User factories
Factory.define :user do |f|
  f.user_name             'nag-o-meter'
  f.first_name            'John'
  f.last_name             'Doe'
  f.dob                   Date.new(1982, 5, 11)
  f.sequence(:email)      {|n| "person#{n}@example.com" }
  f.password              'this_one_goes_to_eleven'
  f.password_confirmation { |u| u.password }
  f.accept_tos            '1'
  f.active                '1'
  f.newsletter            '1'
  f.monthly_nagging       '1'
end

spec out put

1)
Spec::Mocks::MockExpectationError in 'User integrating with mailchimp API should create a working hominid object if user opts-in to the newsletter'
<Hominid (class)> expected :new with (any args) once, but received it 0 times
./spec/models/user_spec.rb:127:

Finished in 1.291039 seconds

user.rb

class User < ActiveRecord::Base
  after_create :check_against_mailchimp

  def add_to_mail_chimp
    @hominid = Hominid.new
    # do more stuff here once we know we have an object being instantiated
  end

  def check_against_mailchimp
      add_to_mail_chimp if newsletter?
  end

end

user_spec.rb

describe User, "integrating with mailchimp API" do

  before :each do
    @user = Factory.create(:user)
  end

  it "should create a working hominid object if user opts-in to the newsletter" do
    Hominid.should_receive(:new)  
  end
  
  it "should send the user's details to mail chimp on sign up if they optin" do
    pending
  end

  it "should not send details to mailchimp if they opt-out" do
    pending
  end

end