test nodelist (#418)

* test nodelist

* usings

* nodelist

---------

BitFaster.Caching.UnitTests/Lfu/LfuNodeListTests.cs

@@ -0,0 +1,56 @@
+using BitFaster.Caching.Lfu;
+using FluentAssertions;
+using Xunit;
+
+namespace BitFaster.Caching.UnitTests.Lfu
+{
+    public class LfuNodeListTests
+    {
+        [Fact]
+        public void WhenPreviousNullLastReturnsNull()
+        {
+            var list = new LfuNodeList<int, int>();
+
+            list.Last.Should().BeNull();
+        }
+
+        [Fact]
+        public void WhenPreviousExistsLastReturnsPrevious()
+        {
+            var list = new LfuNodeList<int, int>();
+            var node1 = new LfuNode<int, int>(1, 1);
+            var node2 = new LfuNode<int, int>(2, 2);
+
+            list.AddLast(node1);
+            list.AddLast(node2);
+
+            list.Last.Should().BeSameAs(node2);
+        }
+
+        [Fact]
+        public void WhenPreviousExistsNodePreviousReturnsPrevious()
+        {
+            var list = new LfuNodeList<int, int>();
+            var node1 = new LfuNode<int, int>(1, 1);
+            var node2 = new LfuNode<int, int>(2, 2);
+
+            list.AddLast(node1);
+            list.AddLast(node2);
+
+            node2.Previous.Should().BeSameAs(node1);
+        }
+
+        [Fact]
+        public void WhenHeadNodePreviousReturnsNull()
+        {
+            var list = new LfuNodeList<int, int>();
+            var node1 = new LfuNode<int, int>(1, 1);
+            var node2 = new LfuNode<int, int>(2, 2);
+
+            list.AddLast(node1);
+            list.AddLast(node2);
+
+            node1.Previous.Should().BeNull();
+        }
+    }
+}

BitFaster.Caching/AssemblyInfo.cs

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+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("BitFaster.Caching.UnitTests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f55849315b02d525d40701eee5d8eba39e6a517644e8af3fa15141eab7058e76be808e36cfee8d7e071b5aac37bd5e45c67971602680f7bfc26d8c9ebca95dd33b4e3f17a4c28b01268ee6b110ad7e2106ab8ffd1c7be3143192527ce5f639395e46ab086518e881706c6ee9eb96f0263aa34e5152cf5aecf657d463fecf62ca")]