diff --git a/eng/build.ps1 b/eng/build.ps1
index f81ad5b3afd899187e3a0cdf74f3dbe3c87e2662..ee79989b58ba2f379fb8da8c30d6550b6e714e85 100644
--- a/eng/build.ps1
+++ b/eng/build.ps1
@@ -212,7 +212,7 @@ function BuildSolution() {
   $projects = Join-Path $RepoRoot $solution
   $toolsetBuildProj = InitializeToolset
 
-  $testTargetFrameworks = if ($testCoreClr) { "netcoreapp3.1" } else { "" }
+  $testTargetFrameworks = if ($testCoreClr) { 'net5.0%3Bnetcoreapp3.1' } else { "" }
   
   $ibcDropName = GetIbcDropName
 
@@ -406,6 +406,7 @@ function TestUsingOptimizedRunner() {
 
   # Exclude out the multi-targetted netcore app projects
   $dlls = $dlls | ?{ -not ($_.FullName -match ".*netcoreapp.*") }
+  $dlls = $dlls | ?{ -not ($_.FullName -match ".*net5.0.*") }
 
   # Exclude out the ref assemblies
   $dlls = $dlls | ?{ -not ($_.FullName -match ".*\\ref\\.*") }
diff --git a/eng/build.sh b/eng/build.sh
index 3dfb1abe19534c6f79e35df3e3fd8e78abbd8691..30a6fbd1f8e24eafc000ccbbfc5c19d452c1fc1d 100755
--- a/eng/build.sh
+++ b/eng/build.sh
@@ -266,7 +266,7 @@ function BuildSolution {
     test_runtime_args="--debug"
   elif [[ "$test_core_clr" == true ]]; then
     test=true
-    test_runtime="/p:TestRuntime=Core /p:TestTargetFrameworks=netcoreapp3.1"
+    test_runtime="/p:TestRuntime=Core /p:TestTargetFrameworks=net5.0%3Bnetcoreapp3.1"
     mono_tool=""
   fi
 
diff --git a/eng/targets/Settings.props b/eng/targets/Settings.props
index 229d6f3a93c1828c533ea1b866d29307982a448d..f17b08fdc703c00aed45cbebae24ff9a6ff2405d 100644
--- a/eng/targets/Settings.props
+++ b/eng/targets/Settings.props
@@ -65,7 +65,7 @@
       These may be overridden by projects that need to be skipped.
     -->
     <TestTargetFrameworks Condition="'$(TestRuntime)' == 'Mono'">net46;net472</TestTargetFrameworks>
-    <TestTargetFrameworks Condition="'$(TestRuntime)' == 'Core'">netcoreapp3.1</TestTargetFrameworks>
+    <TestTargetFrameworks Condition="'$(TestRuntime)' == 'Core'">netcoreapp3.1;net5.0</TestTargetFrameworks>
 
     <XUnitDesktopSettingsFile>$(MSBuildThisFileDirectory)..\config\xunit.runner.json</XUnitDesktopSettingsFile>
     <XUnitCoreSettingsFile>$(MSBuildThisFileDirectory)..\config\xunit.runner.json</XUnitCoreSettingsFile>
diff --git a/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs b/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
index c857d2344fe5353f0e8556334d709495df031996..37cc427d8de2691016e070e78ddcd67d8ef7df2a 100644
--- a/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
+++ b/src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs
@@ -40,7 +40,7 @@ namespace Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests
 {
     public class CommandLineTests : CommandLineTestBase
     {
-#if NETCOREAPP3_1
+#if NETCOREAPP
         private static readonly string s_CSharpCompilerExecutable;
         private static readonly string s_DotnetCscRun;
 #else
@@ -55,7 +55,7 @@ public class CommandLineTests : CommandLineTestBase
 
         static CommandLineTests()
         {
-#if NETCOREAPP3_1
+#if NETCOREAPP
             var cscDllPath = Path.Combine(
                 Path.GetDirectoryName(typeof(CommandLineTests).GetTypeInfo().Assembly.Location),
                 Path.Combine("dependency", "csc.dll"));
diff --git a/src/Compilers/CSharp/Test/CommandLine/Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests.csproj b/src/Compilers/CSharp/Test/CommandLine/Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests.csproj
index 4d7e9cd2bd7c18ee70c3cf648364064745bd19c1..27f18f7217b0ae4e5df9cc8d9cfd5206fcbbe861 100644
--- a/src/Compilers/CSharp/Test/CommandLine/Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/CommandLine/Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.CommandLine.UnitTests</RootNamespace>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <GenerateMicrosoftCodeAnalysisCommitHashAttribute>true</GenerateMicrosoftCodeAnalysisCommitHashAttribute>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/Compilers/CSharp/Test/Emit/Microsoft.CodeAnalysis.CSharp.Emit.UnitTests.csproj b/src/Compilers/CSharp/Test/Emit/Microsoft.CodeAnalysis.CSharp.Emit.UnitTests.csproj
index 625b7be3e1377ba414a03aff422afb2850808468..ec0cda63c4f1c70a593b6155737161d35766a5d5 100644
--- a/src/Compilers/CSharp/Test/Emit/Microsoft.CodeAnalysis.CSharp.Emit.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/Emit/Microsoft.CodeAnalysis.CSharp.Emit.UnitTests.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.UnitTests</RootNamespace>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
diff --git a/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj b/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
index 614ec6dec028c81c0dea6dc18c10343cc62a6210..7346c1eeb7bab5d473e2e6d380f685c847936f81 100644
--- a/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/IOperation/Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.IOperation.UnitTests</RootNamespace>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
     <ProjectReference Include="..\..\..\..\Test\Utilities\Portable\Roslyn.Test.Utilities.csproj" />
diff --git a/src/Compilers/CSharp/Test/Semantic/Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests.csproj b/src/Compilers/CSharp/Test/Semantic/Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests.csproj
index d768bd07eff33da0eec9d3ffe7677017851b1e3f..a388a889b72cd437d521783c91ab0baa22f64ae4 100644
--- a/src/Compilers/CSharp/Test/Semantic/Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/Semantic/Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests.csproj
@@ -4,7 +4,7 @@
   <PropertyGroup>
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.Semantic.UnitTests</RootNamespace>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
     <ProjectReference Include="..\..\..\..\Test\Utilities\Portable\Roslyn.Test.Utilities.csproj" />
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/NativeIntegerTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/NativeIntegerTests.cs
index 0b8b89d2340cd2e560ffee6e486c345e27d10139..b28aab13ba751fbc15c4685b24c42dd5635070fa 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/NativeIntegerTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/NativeIntegerTests.cs
@@ -16,6 +16,7 @@
 using Roslyn.Test.Utilities;
 using Roslyn.Utilities;
 using Xunit;
+using ReferenceEqualityComparer = Roslyn.Utilities.ReferenceEqualityComparer;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests.Semantics
 {
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/OutVarTests.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/OutVarTests.cs
index e68ad76ec08e2ea4c60cd099ccfde1f14e8b930a..1a310e687ddf1265ec87003ce84b55f9975014d1 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/OutVarTests.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/OutVarTests.cs
@@ -16,6 +16,7 @@
 using Roslyn.Utilities;
 using Microsoft.CodeAnalysis.Diagnostics;
 using static Roslyn.Test.Utilities.TestMetadata;
+using ReferenceEqualityComparer = Roslyn.Utilities.ReferenceEqualityComparer;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
 {
diff --git a/src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTestBase.cs b/src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTestBase.cs
index 8419db67dd2b5aef002ba122f9a636ef4d1469ee..fa7d739b766d89d423139eaa62a5d3535ce978bc 100644
--- a/src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTestBase.cs
+++ b/src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTestBase.cs
@@ -12,6 +12,7 @@
 using Roslyn.Test.Utilities;
 using Xunit;
 using Roslyn.Utilities;
+using ReferenceEqualityComparer = Roslyn.Utilities.ReferenceEqualityComparer;
 
 namespace Microsoft.CodeAnalysis.CSharp.UnitTests
 {
diff --git a/src/Compilers/CSharp/Test/Symbol/Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests.csproj b/src/Compilers/CSharp/Test/Symbol/Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests.csproj
index 8677c4fded935a56d56ad97b80bfa37d55e6fed8..e0753bd60f7f9d062b5666c573aa7cff879ba583 100644
--- a/src/Compilers/CSharp/Test/Symbol/Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/Symbol/Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests.csproj
@@ -5,7 +5,7 @@
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CSharp.Symbol.UnitTests</RootNamespace>
     <NoStdLib>true</NoStdLib>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
diff --git a/src/Compilers/CSharp/Test/Syntax/Microsoft.CodeAnalysis.CSharp.Syntax.UnitTests.csproj b/src/Compilers/CSharp/Test/Syntax/Microsoft.CodeAnalysis.CSharp.Syntax.UnitTests.csproj
index 49eef0e4adacd8cdcc200384004d53383ef51157..607a2b9e94c657e8bd43d6bc20c96a23ede5b9f4 100644
--- a/src/Compilers/CSharp/Test/Syntax/Microsoft.CodeAnalysis.CSharp.Syntax.UnitTests.csproj
+++ b/src/Compilers/CSharp/Test/Syntax/Microsoft.CodeAnalysis.CSharp.Syntax.UnitTests.csproj
@@ -7,7 +7,7 @@
     <AllowUnsafeBlocks>false</AllowUnsafeBlocks>
     <NoStdLib>true</NoStdLib>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <!-- The RESX resources generator produces invalid comments when the string has a line starting with '/' -->
     <NoWarn>$(NoWarn);1570;1587</NoWarn>
   </PropertyGroup>
diff --git a/src/Compilers/Core/CodeAnalysisTest/Microsoft.CodeAnalysis.UnitTests.csproj b/src/Compilers/Core/CodeAnalysisTest/Microsoft.CodeAnalysis.UnitTests.csproj
index b1aaf326b54420bfd79503a20118b02d5d6d48a8..6165d42e4f90f60435c28920ccfb29097108323a 100644
--- a/src/Compilers/Core/CodeAnalysisTest/Microsoft.CodeAnalysis.UnitTests.csproj
+++ b/src/Compilers/Core/CodeAnalysisTest/Microsoft.CodeAnalysis.UnitTests.csproj
@@ -5,7 +5,7 @@
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.UnitTests</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup Label="Linked Files">
     <Compile Include="..\..\Shared\GlobalAssemblyCacheHelpers\FusionAssemblyIdentity.cs">
diff --git a/src/Compilers/Core/MSBuildTaskTests/MapSourceRootTests.cs b/src/Compilers/Core/MSBuildTaskTests/MapSourceRootTests.cs
index 08d494495669b54c546828fb43d5ee5d8e919828..1f6153b33f41b79e8b033c28cd2fed4719cc2f24 100644
--- a/src/Compilers/Core/MSBuildTaskTests/MapSourceRootTests.cs
+++ b/src/Compilers/Core/MSBuildTaskTests/MapSourceRootTests.cs
@@ -342,6 +342,7 @@ public void MetadataMerge1(bool deterministic)
                     "MapSourceRoots.ContainsDuplicate", "SourceRoot", path1, "SourceLinkUrl", "URL1", "URL2")) + Environment.NewLine,
                 engine.Log);
 
+            AssertEx.NotNull(task.MappedSourceRoots);
             AssertEx.Equal(new[]
             {
                 $"'{path1}' SourceControl='git' RevisionId='RevId1' NestedRoot='NR1A' ContainingRoot='{path3}' MappedPath='{(deterministic ? "/_/NR1A/" : path1)}' SourceLinkUrl='URL1'",
@@ -446,6 +447,7 @@ public void Error_NoTopLevelSourceRoot(bool deterministic)
             }
             else
             {
+                AssertEx.NotNull(task.MappedSourceRoots);
                 AssertEx.Equal(new[]
                 {
                     $"'{path1}' SourceControl='' RevisionId='' NestedRoot='a/b' ContainingRoot='{path1}' MappedPath='{path1}' SourceLinkUrl=''",
diff --git a/src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj b/src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj
index 91e59ab9621dc636c11baf16cdf37c9655557abf..8e24e13493f4f79fc3d3fadefa566b5a7e64df66 100644
--- a/src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj
+++ b/src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj
@@ -5,7 +5,7 @@
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.BuildTasks.UnitTests</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <Nullable>enable</Nullable>
 
     <!-- Multiple test failures -->
diff --git a/src/Compilers/Core/MSBuildTaskTests/TargetTests.cs b/src/Compilers/Core/MSBuildTaskTests/TargetTests.cs
index c0f6b2e0d021f198e897bd8d87b4725f76dd046a..c7a9ae418599c8753f218277a4c42d6239c0d504 100644
--- a/src/Compilers/Core/MSBuildTaskTests/TargetTests.cs
+++ b/src/Compilers/Core/MSBuildTaskTests/TargetTests.cs
@@ -15,6 +15,7 @@
 using System.Reflection;
 using System.Runtime.CompilerServices;
 using System.Xml;
+using Roslyn.Test.Utilities;
 using Microsoft.Build.Evaluation;
 using Microsoft.Build.Execution;
 using Microsoft.Build.Framework;
@@ -265,15 +266,15 @@ public void GenerateEditorConfigCoreEvaluatesMetadata()
             Assert.Equal("_GeneratedEditorConfigMetadata", item.ItemType);
 
             var itemType = item.Metadata.SingleOrDefault(m => m.Name == "ItemType");
-            Assert.NotNull(itemType);
+            AssertEx.NotNull(itemType);
             Assert.Equal("Compile", itemType.EvaluatedValue);
 
             var metaName = item.Metadata.SingleOrDefault(m => m.Name == "MetadataName");
-            Assert.NotNull(metaName);
+            AssertEx.NotNull(metaName);
             Assert.Equal("CustomMeta", metaName.EvaluatedValue);
 
             var customMeta = item.Metadata.SingleOrDefault(m => m.Name == metaName.EvaluatedValue);
-            Assert.NotNull(customMeta);
+            AssertEx.NotNull(customMeta);
             Assert.Equal("abc", customMeta.EvaluatedValue);
         }
 
@@ -307,15 +308,15 @@ public void GenerateEditorConfigCoreEvaluatesDynamicMetadata()
             Assert.Equal("_GeneratedEditorConfigMetadata", item.ItemType);
 
             var itemType = item.Metadata.SingleOrDefault(m => m.Name == "ItemType");
-            Assert.NotNull(itemType);
+            AssertEx.NotNull(itemType);
             Assert.Equal("Compile", itemType.EvaluatedValue);
 
             var metaName = item.Metadata.SingleOrDefault(m => m.Name == "MetadataName");
-            Assert.NotNull(metaName);
+            AssertEx.NotNull(metaName);
             Assert.Equal("CustomMeta", metaName.EvaluatedValue);
 
             var customMeta = item.Metadata.SingleOrDefault(m => m.Name == metaName.EvaluatedValue);
-            Assert.NotNull(customMeta);
+            AssertEx.NotNull(customMeta);
             Assert.Equal("abc", customMeta.EvaluatedValue);
         }
 
@@ -347,11 +348,11 @@ public void GenerateEditorConfigCoreHandlesMissingMetadata()
             Assert.Equal("_GeneratedEditorConfigMetadata", item.ItemType);
 
             var itemType = item.Metadata.SingleOrDefault(m => m.Name == "ItemType");
-            Assert.NotNull(itemType);
+            AssertEx.NotNull(itemType);
             Assert.Equal("Compile", itemType.EvaluatedValue);
 
             var metaName = item.Metadata.SingleOrDefault(m => m.Name == "MetadataName");
-            Assert.NotNull(metaName);
+            AssertEx.NotNull(metaName);
             Assert.Equal("CustomMeta", metaName.EvaluatedValue);
         }
 
@@ -382,11 +383,11 @@ public void GenerateEditorConfigCoreHandlesMalformedCompilerVisibleItemMetadata(
             Assert.Equal("_GeneratedEditorConfigMetadata", item.ItemType);
 
             var itemType = item.Metadata.SingleOrDefault(m => m.Name == "ItemType");
-            Assert.NotNull(itemType);
+            AssertEx.NotNull(itemType);
             Assert.Equal("Compile", itemType.EvaluatedValue);
 
             var metaName = item.Metadata.SingleOrDefault(m => m.Name == "MetadataName");
-            Assert.NotNull(metaName);
+            AssertEx.NotNull(metaName);
             Assert.Equal("", metaName.EvaluatedValue);
         }
 
diff --git a/src/Compilers/Server/VBCSCompilerTests/VBCSCompiler.UnitTests.csproj b/src/Compilers/Server/VBCSCompilerTests/VBCSCompiler.UnitTests.csproj
index 82b401a580a800c30a969c8b2797a3671624cc7a..a51965c86a11d1571d2fe6a4e6cf1f13d88cf4e4 100644
--- a/src/Compilers/Server/VBCSCompilerTests/VBCSCompiler.UnitTests.csproj
+++ b/src/Compilers/Server/VBCSCompilerTests/VBCSCompiler.UnitTests.csproj
@@ -5,7 +5,7 @@
     <OutputType>Library</OutputType>
     <RootNamespace>Microsoft.CodeAnalysis.CompilerServer.UnitTests</RootNamespace>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
 
     <!-- 
       Currently fails on CI against old versions of mono
@@ -29,8 +29,8 @@
     <ProjectReference Include="..\..\CSharp\Portable\Microsoft.CodeAnalysis.CSharp.csproj" />
   </ItemGroup>
   <ItemGroup>
-    <Reference Include="System" Condition="'$(TargetFramework)' != 'netcoreapp3.1'" />
-    <Reference Include="System.Xml" Condition="'$(TargetFramework)' != 'netcoreapp3.1'" />
+    <Reference Include="System" Condition="'$(TargetFramework)' != 'net5.0'" />
+    <Reference Include="System.Xml" Condition="'$(TargetFramework)' != 'net5.0'" />
     <PackageReference Include="Microsoft.DiaSymReader" Version="$(MicrosoftDiaSymReaderVersion)" />
     <PackageReference Include="Moq" Version="$(MoqVersion)" />
   </ItemGroup>
diff --git a/src/Compilers/VisualBasic/Test/Emit/Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests.vbproj b/src/Compilers/VisualBasic/Test/Emit/Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests.vbproj
index 309eefc2ead4602c4addf47677ec19079cef402d..4d636ef5b53445c96de9a8ab055f4123c0c4fc5e 100644
--- a/src/Compilers/VisualBasic/Test/Emit/Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests.vbproj
+++ b/src/Compilers/VisualBasic/Test/Emit/Microsoft.CodeAnalysis.VisualBasic.Emit.UnitTests.vbproj
@@ -3,7 +3,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <RootNamespace></RootNamespace>
 
     <!-- Disabling on assumption -->
diff --git a/src/Compilers/VisualBasic/Test/IOperation/Roslyn.Compilers.VisualBasic.IOperation.UnitTests.vbproj b/src/Compilers/VisualBasic/Test/IOperation/Roslyn.Compilers.VisualBasic.IOperation.UnitTests.vbproj
index 5cb7be9c6df0e2c06b906fad58cb2b52e879425b..7813c56ae51e110bb789812323e5668ce8d5e9b7 100644
--- a/src/Compilers/VisualBasic/Test/IOperation/Roslyn.Compilers.VisualBasic.IOperation.UnitTests.vbproj
+++ b/src/Compilers/VisualBasic/Test/IOperation/Roslyn.Compilers.VisualBasic.IOperation.UnitTests.vbproj
@@ -3,7 +3,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <RootNamespace></RootNamespace>
   </PropertyGroup>
   <ItemGroup Label="Project References">
diff --git a/src/Compilers/VisualBasic/Test/Semantic/Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj b/src/Compilers/VisualBasic/Test/Semantic/Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj
index 5224f9fa766c69880e2c66bb75d9ee32cd8bb5dd..834db09c0714a91d0a1f505e6bcff8e571e50346 100644
--- a/src/Compilers/VisualBasic/Test/Semantic/Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj
+++ b/src/Compilers/VisualBasic/Test/Semantic/Microsoft.CodeAnalysis.VisualBasic.Semantic.UnitTests.vbproj
@@ -3,7 +3,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <RootNamespace></RootNamespace>
 
     <!--
@@ -28,7 +28,7 @@
     <ProjectReference Include="..\..\Portable\Microsoft.CodeAnalysis.VisualBasic.vbproj" />
   </ItemGroup>
   <ItemGroup>
-    <PackageReference Include="System.Drawing.Common" Version="$(SystemDrawingCommonVersion)" Condition="$(TargetFramework) == 'netcoreapp3.1'" />
+    <PackageReference Include="System.Drawing.Common" Version="$(SystemDrawingCommonVersion)" Condition="$(TargetFramework) == 'net5.0'" />
   </ItemGroup>
   <ItemGroup>
     <Folder Include="My Project\" />
diff --git a/src/Compilers/VisualBasic/Test/Symbol/Microsoft.CodeAnalysis.VisualBasic.Symbol.UnitTests.vbproj b/src/Compilers/VisualBasic/Test/Symbol/Microsoft.CodeAnalysis.VisualBasic.Symbol.UnitTests.vbproj
index bdb3bbf425cc90315cd64effe5715ffc5d1209a0..7a50e5038803364b8cfeb62e8e250c9fac6517d7 100644
--- a/src/Compilers/VisualBasic/Test/Symbol/Microsoft.CodeAnalysis.VisualBasic.Symbol.UnitTests.vbproj
+++ b/src/Compilers/VisualBasic/Test/Symbol/Microsoft.CodeAnalysis.VisualBasic.Symbol.UnitTests.vbproj
@@ -3,7 +3,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
     <RootNamespace></RootNamespace>
 
     <!-- A zillion test failures + crash. See https://github.com/mono/mono/issues/10756. -->
diff --git a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/InstantiatingGenerics.vb b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/InstantiatingGenerics.vb
index 5d1309d8553033a30d635953ddb91727564e89d9..dac4e2057400e72752180014e419f0154817f690 100644
--- a/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/InstantiatingGenerics.vb
+++ b/src/Compilers/VisualBasic/Test/Symbol/SymbolsTests/InstantiatingGenerics.vb
@@ -11,7 +11,7 @@ Imports Microsoft.CodeAnalysis.VisualBasic
 Imports Microsoft.CodeAnalysis.VisualBasic.Symbols
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 Imports Roslyn.Test.Utilities
-
+Imports ReferenceEqualityComparer = Roslyn.Utilities.ReferenceEqualityComparer
 
 Namespace Microsoft.CodeAnalysis.VisualBasic.UnitTests.Symbols
 
diff --git a/src/Compilers/VisualBasic/Test/Syntax/Microsoft.CodeAnalysis.VisualBasic.Syntax.UnitTests.vbproj b/src/Compilers/VisualBasic/Test/Syntax/Microsoft.CodeAnalysis.VisualBasic.Syntax.UnitTests.vbproj
index d5430086b3d1d35b085c7da60935e6b9a71fdb8c..ff75b93c9703b4fd781f0689106a478b03f0fe46 100644
--- a/src/Compilers/VisualBasic/Test/Syntax/Microsoft.CodeAnalysis.VisualBasic.Syntax.UnitTests.vbproj
+++ b/src/Compilers/VisualBasic/Test/Syntax/Microsoft.CodeAnalysis.VisualBasic.Syntax.UnitTests.vbproj
@@ -3,7 +3,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <OutputType>Library</OutputType>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;net472</TargetFrameworks>
   </PropertyGroup>
   <ItemGroup Label="Project References">
     <ProjectReference Include="..\..\..\..\Test\Utilities\Portable\Roslyn.Test.Utilities.csproj" />
diff --git a/src/Test/Utilities/Portable/Assert/AssertEx.cs b/src/Test/Utilities/Portable/Assert/AssertEx.cs
index 18a2b6a5ceb5fc07184849fb56f6ca68d133f693..ffbdb4fd0f3ddc130c4d8b2bc9bf2b36e894eccd 100644
--- a/src/Test/Utilities/Portable/Assert/AssertEx.cs
+++ b/src/Test/Utilities/Portable/Assert/AssertEx.cs
@@ -6,6 +6,8 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Immutable;
+using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection;
@@ -793,5 +795,14 @@ public static void Equal<T>(T[,] expected, Func<int, int, T> getResult, Func<T,
                 Assert.True(false, builder.ToString());
             }
         }
+
+#nullable enable
+        public static void NotNull<T>([NotNull] T value)
+        {
+            Assert.NotNull(value);
+            Debug.Assert(value is object);
+        }
+
+#nullable disable
     }
 }
diff --git a/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj b/src/Workspaces/CoreTestUtilities/Roslyn.Services.UnitTests.Utilities.csproj
index ef2474dc401e2b88aed66e45544520132c902536..55df11539446abb18a8b1015235dab18f7bcffe1 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>
-    <TargetFrameworks>netcoreapp3.1;net472</TargetFrameworks>
+    <TargetFrameworks>net5.0;netcoreapp3.1;net472</TargetFrameworks>
     <UseWpf>true</UseWpf>
     <IsShipping>false</IsShipping>
     <ExcludeFromSourceBuild>true</ExcludeFromSourceBuild>