def test_total_price_when_not_empty(self):
cart = CartFactory()
book1 = BookFactory()
book2 = BookFactory()
cart.items.create(book=book1, quantity=1)
cart.items.create(book=book2, quantity=2)
price = book1.price + book2.price * 2
self.assertEqual(cart.total_price(), price)
def test_total_price_when_empty(self):
cart = CartFactory()
self.assertEqual(cart.total_price(), 0)