associations give unexpected result during rspec test

hello group,

I recently started with the pragmatic bookshelve rspec book. In one of
the latest chapters, there is an example based on the models
'message' and 'user'.

A message has a recipient and an sender. Users have an association
'sent_messages' and 'received_messages'. After the example the book
invites to add a 'subscription' model. A user has one subscription and
it should be possible via the subscription to limit the number of
messages a user can send.

I tried to extend the working rspec examples by adding the
subscription model, but the examples showed me that the associations I
created were not working as I expected. I hope someone can explain me
why.

The code of the models is:

class User < ActiveRecord::Base
    has_many( :received_messages, {:class_name => Message.name,
            :foreign_key => 'recipient_id'})
    has_many( :sent_messages, { :class_name => Message.name,
            :foreign_key => 'sender_id' })
    belongs_to :subscription, :class_name => 'Subscription' # I added
this myself

    def send_message( attrs)
        if subscription.can_send_message?
            sent_messages.create! attrs
        end
    end
end

class Message < ActiveRecord::Base
    belongs_to :recipient, :class_name => 'User'
    validates_presence_of :title, :text, :recipient
end

class Subscription < ActiveRecord::Base # I added this class myself
    has_one( :user, { :class_name => User.name,
            :foreign_key => 'subscription_id' })

    def can_send_message? ()
        puts "size =#{user.sent_messages.size}" # strange. TODO
        user.sent_messages.length < month_limit
    end
end

Now, the example I made to test it is not working: if I access the
sent_messages association via the user directly, I get the expected
messages, but if I do it via the user of the subscription, the
association is an empty array.

To show it, I put some print statements in the example. I'm very much
confused. Who can explain what I did wrong?

describe Subscription do
    describe "#can_send_message?" do
        before( :each) do
            @ruud = User.create! :subscription => Subscription.create!
(
                                                :month_limit => 1),
                                :login => 'rudd'
            @erik = User.create!
        end

        context "when a user has reached the subscription limit for
the month" do
            it "returns false" do
                msg = @ruud.send_message(
                                    :title => "Book Update",
                                    :text => "Beta 11 includes great
stuff!",
                                    :recipient => @erik)
                p @ruud # << this is the test user
                p @ruud.sent_messages
                user_via_subscr = @ruud.subscription.user
                p user_via_subscr # << the test user, accessed
via the subscription
                p user_via_subscr.sent_messages
                @ruud.zent_messages.should == [msg]
                @ruud.subscription.can_send_message?.should == false
            end
        end
    end
end

The output is

size =0
.size =0
#<User id: 1, login: "rudd", created_at: "2012-01-02 10:40:32",
updated_at: "2012-01-02 10:40:32", subscription_id: 1>
[#<Message id: 1, title: "Book Update", text: "Beta 11 includes great
stuff!", recipient_id: 2, created_at: "2012-01-02 10:40:32",
updated_at: "2012-01-02 10:40:32", sender_id: 1>]
#<User id: 1, login: "rudd", created_at: "2012-01-02 10:40:32",
updated_at: "2012-01-02 10:40:32", subscription_id: 1>
[]
size =0

As you can see, if I access the user directly or I access the user via
the subscription, p prints the same fields. But the sent_messages
array is different in both cases......

thanks in advance!

Ruud