Specify models attributes that must not be mass assignated

app/models/playlist.rb

@@ -1,6 +1,8 @@
 class Playlist < ActiveRecord::Base
   belongs_to :user
 
+  attr_accessible :name
+
   validates_presence_of :user
   validates_presence_of :name
 end

spec/models/playlist_spec.rb

@@ -8,4 +8,5 @@ describe Playlist do
   it { should belong_to :user }
   it { should validate_presence_of :user }
   it { should validate_presence_of :name }
+  it { should_not allow_mass_assignment_of :user }
 end

spec/models/track_spec.rb

@@ -8,6 +8,7 @@ describe Track do
   it { should be_valid }
   it { should have_many :sounds }
   it { should validate_presence_of :name }
+  it { should_not allow_mass_assignment_of :sounds }
 
   context 'with a file' do
     before do

spec/models/user_spec.rb

@@ -9,6 +9,7 @@ describe User do
   it { should validate_presence_of :email }
   it { should validate_presence_of :password }
   it { should validate_presence_of :password_hash }
+  it { should_not allow_mass_assignment_of :password_hash }
 
   context 'when a user with the same email address already exists' do
     let(:old_user)  { Factory.create(:user, :email => 'unique@example.net') }