def test_add_remove(list_of_books):
cart = ShoppingCart()
for book in list_of_books:
cart.add(book)
cart.remove(book)
assert cart.total == 0.00
def test_add_remove(example_book):
cart = ShoppingCart()
cart.add(example_book)
cart.remove(example_book)
assert cart.total == 0.00
