Meanwhile, in a large bowl, combine the spinach with the chopped celery.
Add in the cranberries and a can of drained mandarin oranges.
In a small bowl, toss the apple with lemon juice and then add to the salad.
Pour dressing over the salad and toss.
Add in the completely cooled pasta and toss with the rest of the salad.
If you want to toast the pecans, place them in a single layer in a dry saucepan, over medium heat.
Stir constantly until the nuts are barely fragrant; just a couple minutes.
Watch carefully as the nuts are very easily scorched/burned.
Alternatively, you can candy the pecans, if desired.
Top the salad with the pecans and feta cheese.