public async Task DeleteByModel(Topping topping, Topping other)
        {
            await Toppings.AddMany(topping, other);

            await Toppings.Delete(topping);

            var results = (await Toppings.GetAll()).ToList();

            Assert.Single(results);
            Assert.Contains(other, results);
            Assert.DoesNotContain(topping, results);
        }