Associate a user to his playlists

spec/factories.rb

@@ -1,6 +1,7 @@
 FactoryGirl.define do
   factory :playlist do
     name 'Electro'
+    association :user
   end
 
   factory :track do

spec/models/playlist_spec.rb

@@ -2,7 +2,7 @@ require 'spec_helper'
 
 describe Playlist do
   subject { playlist }
-  let(:playlist) { Factory.build(:playlist) }
+  let(:playlist)  { Factory.build(:playlist) }
 
   context 'with valid attributes' do
     it { should be_valid }
@@ -15,4 +15,20 @@ describe Playlist do
 
     it { should_not be_valid }
   end
+
+  context 'without user_id' do
+    before do
+      playlist.user = nil
+    end
+
+    it { should_not be_valid }
+  end
+
+  describe '#user' do
+    it 'returns the user who created the playlist' do
+      user = Factory.create(:user)
+      playlist = user.playlists.build(Factory.attributes_for(:playlist))
+      playlist.user.should == user
+    end
+  end
 end