ConcurrentLfu time-based expiry

BitFaster.Caching.UnitTests/Lfu/TimerWheelTests.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using BitFaster.Caching.Lfu;
+using BitFaster.Caching.Lru;
+using BitFaster.Caching.Scheduler;
+using FluentAssertions;
+using Xunit;
+
+namespace BitFaster.Caching.UnitTests.Lfu
+{
+    public class TimerWheelTests
+    {
+        [Fact]
+        public void Test()
+        {
+            var wheel = new TimerWheel<int, int, TimeOrderNode<int, int>, ExpireAfterPolicy<int, int>>();
+            var policy = new ExpireAfterPolicy<int, int>(wheel);
+            var cache = new ConcurrentLfuCore<int, int, TimeOrderNode<int, int>, ExpireAfterPolicy<int, int>>(
+                Defaults.ConcurrencyLevel, 3, new ThreadPoolScheduler(), EqualityComparer<int>.Default, () => { }, policy);
+
+            wheel.Should().NotBeNull();
+        }
+    }
+}

BitFaster.Caching/ItemRemovedReason.cs

@@ -30,5 +30,7 @@
         /// The item was removed from the cache by a trim method call.
         /// </summary>
         Trimmed,
+
+        Expired,
     }
 }