capacity

Author: Alex Peck

BitFaster.Caching.UnitTests/Lfu/ConcurrentLfuTests.cs

@@ -26,6 +26,30 @@ public ConcurrentLfuTests(ITestOutputHelper output)
             this.output = output;
         }
 
+        [Fact]
+        public void WhenCapacityIsLessThan3CtorThrows()
+        {
+            Action constructor = () => { var x = new ConcurrentLfu<int, string>(2); };
+
+            constructor.Should().Throw<ArgumentOutOfRangeException>();
+        }
+
+        [Fact]
+        public void WhenCapacityIsValidCacheIsCreated()
+        {
+            var x = new ConcurrentLfu<int, string>(3);
+
+            x.Capacity.Should().Be(3);
+        }
+
+        [Fact]
+        public void WhenConcurrencyIsLessThan1CtorThrows()
+        {
+            Action constructor = () => { var x = new ConcurrentLfu<int, string>(0, 20, new ForegroundScheduler(), EqualityComparer<int>.Default); };
+
+            constructor.Should().Throw<ArgumentOutOfRangeException>();
+        }
+
         [Fact]
         public void DefaultSchedulerIsThreadPool()
         {

BitFaster.Caching/Lfu/ConcurrentLfu.cs

@@ -309,6 +309,9 @@ internal struct ConcurrentLfuCore<K, V, N, P> : ICache<K, V>, IAsyncCache<K, V>,
 
         public ConcurrentLfuCore(int concurrencyLevel, int capacity, IScheduler scheduler, IEqualityComparer<K> comparer, Action drainBuffers)
         {
+            if (capacity < 3)
+                Throw.ArgOutOfRange(nameof(capacity));
+
             int dictionaryCapacity = ConcurrentDictionarySize.Estimate(capacity);
             this.dictionary = new (concurrencyLevel, dictionaryCapacity, comparer);