def test_added_books_change(self):
        """
        Must save book page after changing it.
        """
        added_book3 = AddedBook.objects.get(id_user=self.the_user1, id_book=Book.objects.get(book_name='Third Book'))
        added_book6 = AddedBook.objects.get(id_user=self.the_user2, id_book=Book.objects.get(book_name='Sixth Book'))
        self.assertEqual(added_book3.last_page, 1)
        self.assertEqual(added_book6.last_page, 1)

        added_book3.last_page = 500
        added_book3.save()
        self.assertEqual(added_book3.last_page, 500)
        self.assertEqual(added_book6.last_page, 1)

        added_book6.last_page = 256
        added_book6.save()
        self.assertEqual(added_book3.last_page, 500)
        self.assertEqual(added_book6.last_page, 256)