Bundle shoulda and use ActiveModel matchers in specs

spec/models/playlist_spec.rb

@@ -1,34 +1,11 @@
 require 'spec_helper'
 
 describe Playlist do
-  subject { playlist }
+  subject         { playlist }
   let(:playlist)  { Factory.build(:playlist) }
 
-  context 'with valid attributes' do
-    it { should be_valid }
-  end
-
-  context 'when name empty' do
-    before do
-      playlist.name = ''
-    end
-
-    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
+  it { should be_valid }
+  it { should belong_to :user }
+  it { should validate_presence_of :user }
+  it { should validate_presence_of :name }
 end