In a large stockpot, heat one teaspoon olive oil. Add the onions, celery, and carrots. Saute for 8-10 minutes until the vegetables are translucent.
Add the garlic and cook for one minute.
Add the meatballs, stock, tomatoes, beans, and seasonings to the pot. Bring to a boil, reduce the heat, and simmer for 15-20 minutes.
Stir in the spinach and cook for another 5 minutes.
Just prior to serving, add the cooked pasta and let it heat through.