public async Task GetManyByParam(Pizza a, Pizza b, Pizza c)
        {
            await Pizzas.AddMany(a, b, c);

            var results = (await Pizzas.GetMany(a.Id, c.Id)).ToList();

            Assert.Equal(2, results.Count);
            Assert.Contains(a, results);
            Assert.DoesNotContain(b, results);
            Assert.Contains(c, results);
        }
        public async Task GetManyByEnumerable(List <Pizza> ps, Pizza exclude)
        {
            await Pizzas.Add(exclude);

            await Pizzas.AddMany(ps);

            var results = (await Pizzas.GetMany(ps.Select(p => p.Id))).ToList();

            Assert.Equal(ps.Count, results.Count);
            Assert.All(ps, p => Assert.Contains(p, results));
            Assert.DoesNotContain(exclude, results);
        }