BlockingCollection with priorities

gistfile1.cs

public class PriorityCollection
    {
        private readonly BlockingCollection<Item> low = new BlockingCollection<Item>();
        private readonly BlockingCollection<Item> middle = new BlockingCollection<Item>();
        private readonly BlockingCollection<Item> high = new BlockingCollection<Item>();
        private readonly BlockingCollection<Guid> main = new BlockingCollection<Guid>(); 
        private readonly BlockingCollection<Item>[] queue;
        private readonly Dictionary<Priority, BlockingCollection<Item>> priorityMap = new Dictionary<Priority, BlockingCollection<Item>>();
        public List<Priority> TestList { get; private set; }

        public PriorityCollection()
        {
            queue = new[]{high, middle, low};
            TestList = new List<Priority>();
            priorityMap.Add(Priority.Low, low);
            priorityMap.Add(Priority.Middle, middle);
            priorityMap.Add(Priority.High, high);
        }

        public void Publish(Item item)
        {
            var guid = Guid.NewGuid();
            priorityMap[item.Priority].Add(item);
            main.Add(guid);
            Console.Out.WriteLine("item with priority {0} is published", item.Priority);
        }

        public void ProcessItems(CancellationToken token)
        {
            foreach (var guid in main.GetConsumingEnumerable(token))
            {
                Item item;
                BlockingCollection<Item>.TakeFromAny(queue, out item);
                var priority = item.Priority;
                Console.Out.WriteLine("item with priority {0} is processed", priority);
                TestList.Add(priority);
            }
        }
    }

    public enum Priority
    {
        High,
        Middle,
        Low
    }
    
    public class Item
    {
       public Priority Priority { get; set; }
    }
    
    public class PriorityCollectionTests
    {
        [Fact]
        public void should_process_items_by_their_priorities()
        {
            var token = new CancellationTokenSource();
            var priorityCollection = new PriorityCollection();
            Task.Factory.ContinueWhenAll(new[]
                                             {
                                                 Task.Factory.StartNew(() => priorityCollection.ProcessItems(token.Token)),
                                                 GenerateItems(priorityCollection, Priority.Low),
                                                 GenerateItems(priorityCollection, Priority.High),
                                                 GenerateItems(priorityCollection, Priority.Middle)
                                             }, tasks => { });
            Thread.Sleep(5000);
            token.Cancel();

            priorityCollection.TestList.Should().ContainInOrder(
                Enumerable.Range(0, 10).Select(i => Priority.High).Union(
                    Enumerable.Range(0, 10).Select(i => Priority.Middle)).Union(
                        Enumerable.Range(0, 10).Select(i => Priority.Low)));
        }

        private static Task GenerateItems(PriorityCollection priorityCollection, Priority priority)
        {
            return Task.Factory.StartNew(() => 
                Enumerable.Range(0, 10).ToList().ForEach(i => priorityCollection.Publish(new Item{Priority = priority})));
        }
    }