Add authentication and User model

* Add User model
* Add SessionsController
* Add password authentication on User
* Request authentication for all actions except sign in
* Add some helpers for ApplicationController
* Update features to work with mandatory authentication

spec/controllers/application_controller_spec.rb

@@ -0,0 +1,21 @@
+require 'spec_helper'
+
+describe ApplicationController do
+  let(:user) { Factory.create(:user) }
+
+  describe '#current_user=' do
+    it 'stores the user id in the session as :user_id' do
+      controller.current_user = user
+      session[:user_id].should == user.id
+    end
+  end
+
+  describe '#current_user' do
+    context 'when session[:user_id] is set' do
+      it 'returns the User instance from the session' do
+        session[:user_id] = user.id
+        controller.current_user.should == user
+      end
+    end
+  end
+end

spec/controllers/home_controller_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe HomeController do
+  before do
+    controller.current_user = Factory.create(:user)
+  end
+
   describe 'GET index' do
     it 'assigns all playlists as @playlists' do
       playlist = Factory.create(:playlist)

spec/controllers/playlists_controller_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe PlaylistsController do
+  before do
+    controller.current_user = Factory.create(:user)
+  end
+
   describe 'GET index' do
     it 'assigns all playlists as @playlists' do
       playlist = Factory.create(:playlist)

spec/controllers/sessions_controller_spec.rb

@@ -0,0 +1,40 @@
+require 'spec_helper'
+
+describe SessionsController do
+  describe 'GET new' do
+    it 'responds successfully' do
+      response.should be_success
+    end
+  end
+
+  describe 'POST create' do
+    context 'when the user submit invalid credentials' do
+      it 'renders the new template' do
+        User.stub(:authenticate).and_return(false)
+        post :create,
+          :session => Factory.attributes_for(:user, :password => 'WRONG')
+        response.should render_template('new')
+      end
+    end
+
+    context 'when the user submit valid credentials' do
+      let(:user) { Factory.create(:user) }
+      before do
+        User.stub(:authenticate).and_return(user)
+      end
+
+      it 'signs the user in' do
+        post :create, :session => Factory.attributes_for(:user)
+        controller.current_user.should == user
+      end
+
+      it 'redirects to the home page' do
+        post :create, :session => Factory.attributes_for(:user)
+        response.should redirect_to(:root)
+      end
+    end
+  end
+
+  describe 'DELETE destroy' do
+  end
+end

spec/controllers/tracks_controller_spec.rb

@@ -1,6 +1,10 @@
 require 'spec_helper'
 
 describe TracksController do
+  before do
+    controller.current_user = Factory.create(:user)
+  end
+
   describe 'GET show' do
     it 'assigns the requested track as @track' do
       track = Factory.create(:track)