added test case for deleting music_session

spec/managers/music_session_manager_spec.rb

@@ -39,6 +39,14 @@ describe MusicSessionManager do
       music_session.genres.should == [@genre, genre2]
     end
 
+    it "deletes a session properly" do
+      music_session = @music_session_manager.create(@user, @connection.client_id, "description", true, false, true, true, @band, [@genre], @tracks, true)
+      MusicSessionHistory.count.should == 1
+      MusicSessionHistory.first.music_session_id.should == music_session.id
+      music_session.destroy
+      MusicSessionHistory.first.session_removed_at.should_not == nil
+    end
+    
   end
 
-end
+end