diff --git a/eng/Versions.props b/eng/Versions.props
index a64c502a0df295791b124a03ccf13881801c30e3..e87dc28700e7ea44ef2bc317f7f59d57920d8196 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -30,7 +30,7 @@
     <RoslynDiagnosticsNugetPackageVersion>3.3.0-beta1.20352.4</RoslynDiagnosticsNugetPackageVersion>
     <MicrosoftCodeAnalysisNetAnalyzersVersion>3.3.0-beta1.20352.4</MicrosoftCodeAnalysisNetAnalyzersVersion>
     <CodeStyleLayerCodeAnalysisVersion>3.6.0-2.final</CodeStyleLayerCodeAnalysisVersion>
-    <MicrosoftCodeAnalysisTestingVersion>1.0.1-beta1.20210.2</MicrosoftCodeAnalysisTestingVersion>
+    <MicrosoftCodeAnalysisTestingVersion>1.0.1-beta1.20358.1</MicrosoftCodeAnalysisTestingVersion>
     <CodeStyleAnalyzerVersion>3.7.0-3.20271.4</CodeStyleAnalyzerVersion>
     <VisualStudioEditorPackagesVersion>16.4.248</VisualStudioEditorPackagesVersion>
     <ILToolsPackageVersion>5.0.0-alpha1.19409.1</ILToolsPackageVersion>
@@ -108,7 +108,7 @@
     <MicrosoftVisualStudioCodeAnalysisSdkUIVersion>15.8.27812-alpha</MicrosoftVisualStudioCodeAnalysisSdkUIVersion>
     <MicrosoftVisualStudioCodingConventionsVersion>1.1.20180503.2</MicrosoftVisualStudioCodingConventionsVersion>
     <MicrosoftVisualStudioComponentModelHostVersion>16.0.467</MicrosoftVisualStudioComponentModelHostVersion>
-    <MicrosoftVisualStudioCompositionVersion>15.6.36</MicrosoftVisualStudioCompositionVersion>
+    <MicrosoftVisualStudioCompositionVersion>16.4.11</MicrosoftVisualStudioCompositionVersion>
     <MicrosoftVisualStudioCoreUtilityVersion>$(VisualStudioEditorPackagesVersion)</MicrosoftVisualStudioCoreUtilityVersion>
     <MicrosoftVisualStudioDebuggerUIInterfacesVersion>16.4.0-beta.20106.1</MicrosoftVisualStudioDebuggerUIInterfacesVersion>
     <MicrosoftVisualStudioDebuggerEngineimplementationVersion>16.5.1122001-preview</MicrosoftVisualStudioDebuggerEngineimplementationVersion>
diff --git a/src/Setup/DevDivInsertionFiles/DevDivInsertionFiles.csproj b/src/Setup/DevDivInsertionFiles/DevDivInsertionFiles.csproj
index 1724db82e120830d712865b20a0a99e6325ae4b4..5a1309fbdf4e184353f8eb3f0b6b79e9d06a452f 100644
--- a/src/Setup/DevDivInsertionFiles/DevDivInsertionFiles.csproj
+++ b/src/Setup/DevDivInsertionFiles/DevDivInsertionFiles.csproj
@@ -145,6 +145,7 @@
       <_Dependency Remove="stdole"/>
       <_Dependency Remove="StreamJsonRpc"/>
       <_Dependency Remove="System.IO.Pipelines"/>
+      <_Dependency Remove="System.Reflection.TypeExtensions"/>
       <_Dependency Remove="System.ValueTuple"/>
       <_Dependency Remove="System.Security.AccessControl"/>
       <_Dependency Remove="System.Security.Principal.Windows"/>
diff --git a/src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioMefHostServices.cs b/src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioMefHostServices.cs
index c46cf451cbff839fe1721596ef37324653413bb0..4f85da07739730cf92cb7fbc899c8adcca5c5e16 100644
--- a/src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioMefHostServices.cs
+++ b/src/VisualStudio/Core/Def/Implementation/ProjectSystem/VisualStudioMefHostServices.cs
@@ -48,7 +48,7 @@ protected internal override HostWorkspaceServices CreateWorkspaceServices(Worksp
         /// </summary>
         public IEnumerable<Lazy<TExtension, TMetadata>> GetExports<TExtension, TMetadata>()
         {
-            var key = new ExportKey(typeof(TExtension).AssemblyQualifiedName, typeof(TMetadata).AssemblyQualifiedName);
+            var key = new ExportKey(typeof(TExtension).AssemblyQualifiedName!, typeof(TMetadata).AssemblyQualifiedName!);
             if (!_exportsMap.TryGetValue(key, out var exports))
             {
                 exports = ImmutableInterlocked.GetOrAdd(ref _exportsMap, key, _ =>
@@ -65,7 +65,7 @@ protected internal override HostWorkspaceServices CreateWorkspaceServices(Worksp
         /// </summary>
         public IEnumerable<Lazy<TExtension>> GetExports<TExtension>()
         {
-            var key = new ExportKey(typeof(TExtension).AssemblyQualifiedName, "");
+            var key = new ExportKey(typeof(TExtension).AssemblyQualifiedName!, "");
             if (!_exportsMap.TryGetValue(key, out var exports))
             {
                 exports = ImmutableInterlocked.GetOrAdd(ref _exportsMap, key, _ =>
@@ -90,7 +90,7 @@ public bool Equals(ExportKey other)
                 => string.Compare(ExtensionTypeName, other.ExtensionTypeName, StringComparison.OrdinalIgnoreCase) == 0 &&
                    string.Compare(MetadataTypeName, other.MetadataTypeName, StringComparison.OrdinalIgnoreCase) == 0;
 
-            public override bool Equals(object obj)
+            public override bool Equals(object? obj)
                 => obj is ExportKey key && Equals(key);
 
             public override int GetHashCode()
diff --git a/src/Workspaces/CoreTestUtilities/DotNetCoreSdk.cs b/src/Workspaces/CoreTestUtilities/DotNetCoreSdk.cs
index 4ed2d020fd9ceaf331b95f2ff3cab110c77ab691..2377ede30618ba9fc844d8b3202d809449a54b40 100644
--- a/src/Workspaces/CoreTestUtilities/DotNetCoreSdk.cs
+++ b/src/Workspaces/CoreTestUtilities/DotNetCoreSdk.cs
@@ -27,14 +27,14 @@ static DotNetCoreSdk()
         {
             var dotNetExeName = "dotnet" + (Path.DirectorySeparatorChar == '/' ? "" : ".exe");
 
-            bool DotNetExeExists(string directory)
+            bool DotNetExeExists(string? directory)
                 => directory != null
                 && File.Exists(Path.Combine(directory, dotNetExeName));
 
             var dotNetInstallDir = Environment.GetEnvironmentVariable("DOTNET_INSTALL_DIR");
             if (!DotNetExeExists(dotNetInstallDir))
             {
-                dotNetInstallDir = Environment.GetEnvironmentVariable("PATH")
+                dotNetInstallDir = Environment.GetEnvironmentVariable("PATH")!
                     .Split(Path.PathSeparator)
                     .FirstOrDefault(DotNetExeExists);
             }
diff --git a/src/Workspaces/CoreTestUtilities/OptionsCollection.cs b/src/Workspaces/CoreTestUtilities/OptionsCollection.cs
index d0138cfe13e8e94c87699e4832332e089ae21d4a..14f28f946cf8b16a3a6f4a9a1cbde8464893f9a6 100644
--- a/src/Workspaces/CoreTestUtilities/OptionsCollection.cs
+++ b/src/Workspaces/CoreTestUtilities/OptionsCollection.cs
@@ -4,12 +4,15 @@
 
 #nullable enable
 
-using System;
 using System.Collections;
 using System.Collections.Generic;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.Options;
+
+#if !NETCOREAPP
+using System;
 using Roslyn.Utilities;
+#endif
 
 namespace Microsoft.CodeAnalysis.Editor.UnitTests.CodeActions
 {
diff --git a/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj b/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj
index 66cd300d7a8ddaa454dae7d28dea06c0a12cf3ac..e5d75bf6be84a1cd05ee3007f845f6faf6847253 100644
--- a/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj
+++ b/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.UnitTests</RootNamespace>
-    <TargetFramework>net472</TargetFramework>
+    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
     <UseWpf>true</UseWpf>
     <IsShipping>false</IsShipping>
     <ExcludeFromSourceBuild>true</ExcludeFromSourceBuild>
diff --git a/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext+DenyExecutionSynchronizationContext.cs b/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext+DenyExecutionSynchronizationContext.cs
index 283c2b80fbb1e80310b87a54ec710a24ef60f52b..9da83e390291950cbcae96933ce47abe4c41846e 100644
--- a/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext+DenyExecutionSynchronizationContext.cs
+++ b/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext+DenyExecutionSynchronizationContext.cs
@@ -98,7 +98,7 @@ internal void ThrowIfSwitchOccurred()
                 _failedTransfer.Value.Throw();
             }
 
-            public override void Post(SendOrPostCallback d, object state)
+            public override void Post(SendOrPostCallback d, object? state)
             {
                 try
                 {
@@ -117,7 +117,7 @@ public override void Post(SendOrPostCallback d, object state)
 #pragma warning restore VSTHRD001 // Avoid legacy thread switching APIs
             }
 
-            public override void Send(SendOrPostCallback d, object state)
+            public override void Send(SendOrPostCallback d, object? state)
             {
                 try
                 {
diff --git a/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext.cs b/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext.cs
index 6249b5f79c5533d5a84dd4c519f1449fb3a559a8..cd5e9236d3227bbc359f276859d84be57618dbf8 100644
--- a/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext.cs
+++ b/src/Workspaces/CoreTestUtilities/TestExportJoinableTaskContext.cs
@@ -111,8 +111,8 @@ internal static void ResetThreadAffinity(JoinableTaskFactory joinableTaskFactory
                 var type = assembly.GetType("Microsoft.VisualStudio.Language.Intellisense.Implementation.ForegroundThreadAffinitizedObject", throwOnError: false);
                 if (type != null)
                 {
-                    type.GetField("foregroundThread", BindingFlags.Static | BindingFlags.NonPublic).SetValue(null, thread);
-                    type.GetField("ForegroundTaskScheduler", BindingFlags.Static | BindingFlags.NonPublic).SetValue(null, taskScheduler);
+                    type.GetField("foregroundThread", BindingFlags.Static | BindingFlags.NonPublic)!.SetValue(null, thread);
+                    type.GetField("ForegroundTaskScheduler", BindingFlags.Static | BindingFlags.NonPublic)!.SetValue(null, taskScheduler);
 
                     break;
                 }