Cook sausage until browned. Drain. Stir in onions, mushrooms, and garlic. Saute slightly. Pour in chicken broth, tomato sauce, and diced tomatoes; bring soup to a boil. Stir pasta into the soup. Cook, stirring occasionally, until almost tender, about 10 minutes. Stir in spinach, mozzarella cheese, and parmesan cheese. Remove from heat; stir in basil and let stand until pasta is tender, about 2 more minutes. (If you don't have fresh basil, put some dried basil in with the sauce.)