Add tests for Volatile.ReadBarrier and Volatile.WriteBarrier

src/libraries/System.Threading/tests/System.Threading.Tests.csproj

@@ -34,6 +34,7 @@
     <Compile Include="ReaderWriterLockSlimTests.cs" />
     <Compile Include="SpinWaitTests.cs" />
     <Compile Include="ThreadLocalTests.cs" />
+    <Compile Include="VolatileTests.cs" />
     <Compile Include="XunitAssemblyAttributes.cs" />
     <Compile Include="ExecutionContextTests.cs" />
     <Compile Include="SynchronizationContextTests.cs" />

src/libraries/System.Threading/tests/VolatileTests.cs

@@ -0,0 +1,64 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Reflection;
+using Xunit;
+
+namespace System.Threading.Tests
+{
+    public class VolatileTests
+    {
+        [Fact]
+        public void Barriers_DoNotThrow()
+        {
+            Volatile.ReadBarrier();
+            Volatile.WriteBarrier();
+        }
+
+        [Fact]
+        public void BarriersViaReflection()
+        {
+            MethodInfo readBarrierMethod = typeof(Volatile).GetMethod(nameof(Volatile.ReadBarrier), BindingFlags.Public | BindingFlags.Static);
+            MethodInfo writeBarrierMethod = typeof(Volatile).GetMethod(nameof(Volatile.WriteBarrier), BindingFlags.Public | BindingFlags.Static);
+            Assert.NotNull(readBarrierMethod);
+            Assert.NotNull(writeBarrierMethod);
+            readBarrierMethod.Invoke(null, null);
+            writeBarrierMethod.Invoke(null, null);
+        }
+
+        [Fact]
+        public void BarriersAndVolatileOperations()
+        {
+            int value1 = 0;
+            int value2 = 0;
+            long value3 = 0;
+
+            Volatile.ReadBarrier();
+            Volatile.WriteBarrier();
+
+            Volatile.Write(ref value1, 42);
+            Volatile.WriteBarrier();
+            Assert.Equal(42, value1);
+
+            Volatile.ReadBarrier();
+            int result1 = Volatile.Read(ref value1);
+            Assert.Equal(42, result1);
+
+            Volatile.ReadBarrier();
+            Volatile.ReadBarrier();
+            Volatile.WriteBarrier();
+            Volatile.WriteBarrier();
+
+            Volatile.Write(ref value2, 100);
+            Volatile.WriteBarrier();
+            Volatile.ReadBarrier();
+            int result2 = Volatile.Read(ref value2);
+            Assert.Equal(100, result2);
+
+            Volatile.Write(ref value3, 123456789L);
+            Volatile.ReadBarrier();
+            long result3 = Volatile.Read(ref value3);
+            Assert.Equal(123456789L, result3);
+        }
+    }
+}