Fix playlist/update action behaviour with invalid params

app/controllers/playlists_controller.rb

@@ -22,7 +22,10 @@ class PlaylistsController < ApplicationController
 
   def update
     @playlist = Playlist.find(params[:id])
-    @playlist.update_attributes params[:playlist]
+    if @playlist.update_attributes params[:playlist]
       redirect_to :action => 'index'
+    else
+      render :action => 'edit'
+    end
   end
 end

spec/controllers/playlists_controller_spec.rb

@@ -58,25 +58,37 @@ describe PlaylistsController do
   end
 
   describe 'PUT update' do
+    let (:playlist) { Factory.create(:playlist) }
+
+    def do_update
+      put :update, :id => playlist.id.to_s, :playlist => { :name => 'Rock' }
+    end
+
+    context 'whith valid params' do
       it 'updates the playlist' do
-      playlist = Factory.create(:playlist)
         Playlist.any_instance.should_receive(:update_attributes).
           with({'name' => 'Rock'})
-      put :update, :id => playlist.id.to_s, :playlist => {:name => 'Rock'}
+        do_update
       end
 
-    it 'assigns the requested playlist as @playlist' do
-      playlist = Factory.create(:playlist)
-      put :update, :id => playlist.id.to_s, :playlist => {:name => 'Rock'}
-      assigns[:playlist].should == playlist
-    end
-
-    context 'when the playlist updates successfully' do
       it 'redirects to the playlists index' do
-        playlist = Factory.create(:playlist)
-        put :update, :id => playlist.id.to_s, :playlist => Factory.attributes_for(:playlist)
+        do_update
         response.should redirect_to(:action => 'index')
       end
     end
+
+    context 'with invalid params' do
+      before { Playlist.any_instance.stub(:save).and_return(false) }
+
+      it 'assigns the requested playlist as @playlist' do
+        do_update
+        assigns[:playlist].should == playlist
+      end
+
+      it 'renders the edit template' do
+        do_update
+        response.should render_template('edit')
+      end
+    end
   end
 end