public async Task GetManyParams(Topping a, Topping b, Topping c)
        {
            await Toppings.AddMany(a, b, c);

            var results = (await Toppings.GetMany(b.Id, c.Id)).ToList();

            Assert.Equal(2, results.Count);
            Assert.DoesNotContain(a, results);
            Assert.Contains(b, results);
            Assert.Contains(c, results);
        }
        public async Task GetManyEnumerable(List <Topping> toppings, Topping other)
        {
            await Toppings.AddMany(toppings);

            await Toppings.Add(other);

            var results = (await Toppings.GetMany(toppings.Select(t => t.Id))).ToList();

            Assert.Equal(toppings.Count, results.Count);
            Assert.DoesNotContain(other, results);
            Assert.All(results, t => Assert.Contains(t, toppings));
        }