diff --git a/eng/build-pr.yml b/eng/build-pr.yml
index 831d96781f0a..e9a14cdf7e80 100644
--- a/eng/build-pr.yml
+++ b/eng/build-pr.yml
@@ -233,8 +233,8 @@ jobs:
     - task: PublishTestResults@2
       displayName: Publish Test Results
       inputs:
-        testRunner: XUnit
-        testResultsFiles: 'artifacts/TestResults/${{ parameters.buildConfiguration }}/*.xml'
+        testRunner: VSTest
+        testResultsFiles: 'artifacts/TestResults/${{ parameters.buildConfiguration }}/*.trx'
         testRunTitle: '$(_AgentOSName)_$(Agent.JobName)'
         platform: '$(BuildPlatform)'
         configuration: '${{ parameters.buildConfiguration }}'
diff --git a/eng/build.yml b/eng/build.yml
index 4f947ea8f7ea..d901233c41d0 100644
--- a/eng/build.yml
+++ b/eng/build.yml
@@ -239,8 +239,8 @@ jobs:
     - task: PublishTestResults@2
       displayName: Publish Test Results
       inputs:
-        testRunner: XUnit
-        testResultsFiles: 'artifacts/TestResults/${{ parameters.buildConfiguration }}/*.xml'
+        testRunner: VSTest
+        testResultsFiles: 'artifacts/TestResults/${{ parameters.buildConfiguration }}/*.trx'
         testRunTitle: '$(_AgentOSName)_$(Agent.JobName)'
         platform: '$(BuildPlatform)'
         configuration: '${{ parameters.buildConfiguration }}'
diff --git a/test/Directory.Build.props b/test/Directory.Build.props
index 26d486322e94..8369b6680a26 100644
--- a/test/Directory.Build.props
+++ b/test/Directory.Build.props
@@ -3,5 +3,6 @@
   <Import Project="..\eng\TestVersions.props" />
   <PropertyGroup>
     <ExcludeFromSourceBuild>true</ExcludeFromSourceBuild>
+    <UseVSTestRunner>true</UseVSTestRunner>
   </PropertyGroup>
 </Project>
diff --git a/test/EndToEnd/ValidateInsertedManifests.cs b/test/EndToEnd/ValidateInsertedManifests.cs
index cdede126c997..0b2668afc476 100644
--- a/test/EndToEnd/ValidateInsertedManifests.cs
+++ b/test/EndToEnd/ValidateInsertedManifests.cs
@@ -34,7 +34,7 @@ public void ManifestReaderCanReadManifests()
                     File.Exists(manifestFile).Should().BeTrue();
                     using var fileStream = new FileStream(manifestFile, FileMode.Open, FileAccess.Read);
                     Action readManifest = () => WorkloadManifestReader.ReadWorkloadManifest(manifestId, fileStream, manifestFile);
-                    readManifest.ShouldNotThrow("manifestId:" + manifestId + " manifestFile:" + manifestFile + "is invalid");
+                    readManifest.Should().NotThrow("manifestId:" + manifestId + " manifestFile:" + manifestFile + "is invalid");
                 }
             }
             
diff --git a/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/CommandResultAssertions.cs b/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/CommandResultAssertions.cs
index 7301d9a814a9..2c883c4186d7 100644
--- a/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/CommandResultAssertions.cs
+++ b/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/CommandResultAssertions.cs
@@ -28,14 +28,14 @@ public AndConstraint<CommandResultAssertions> ExitWith(int expectedExitCode)
         public AndConstraint<CommandResultAssertions> Pass()
         {
             Execute.Assertion.ForCondition(_commandResult.ExitCode == 0)
-                .FailWith(AppendDiagnosticsTo($"Expected command to pass but it did not."));
+                .FailWith(AppendDiagnosticsTo("Expected command to pass but it did not."));
             return new AndConstraint<CommandResultAssertions>(this);
         }
 
         public AndConstraint<CommandResultAssertions> Fail()
         {
             Execute.Assertion.ForCondition(_commandResult.ExitCode != 0)
-                .FailWith(AppendDiagnosticsTo($"Expected command to fail but it did not."));
+                .FailWith(AppendDiagnosticsTo("Expected command to fail but it did not."));
             return new AndConstraint<CommandResultAssertions>(this);
         }
 
@@ -125,7 +125,7 @@ public AndConstraint<CommandResultAssertions> HaveStdErrMatching(string pattern,
         public AndConstraint<CommandResultAssertions> NotHaveStdOut()
         {
             Execute.Assertion.ForCondition(string.IsNullOrEmpty(_commandResult.StdOut))
-                .FailWith(AppendDiagnosticsTo($"Expected command to not output to stdout but it was not:"));
+                .FailWith(AppendDiagnosticsTo("Expected command to not output to stdout but it was not:"));
             return new AndConstraint<CommandResultAssertions>(this);
         }
 
diff --git a/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/DirectoryInfoAssertions.cs b/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/DirectoryInfoAssertions.cs
index adb83caf28c2..74b45b8dbc5e 100644
--- a/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/DirectoryInfoAssertions.cs
+++ b/test/Microsoft.DotNet.Tools.Tests.Utilities/Assertions/DirectoryInfoAssertions.cs
@@ -26,7 +26,7 @@ public DirectoryInfoAssertions(DirectoryInfo dir)
         public AndConstraint<DirectoryInfoAssertions> Exist()
         {
             Execute.Assertion.ForCondition(_dirInfo.Exists)
-                .FailWith("Expected directory {0} does not exist.", _dirInfo.FullName);
+                .FailWith(String.Format("Expected directory {0} does not exist.", _dirInfo.FullName));
             return new AndConstraint<DirectoryInfoAssertions>(this);
         }
 
@@ -71,7 +71,7 @@ public AndConstraint<DirectoryInfoAssertions> NotHaveFile(
             Execute.Assertion
                 .ForCondition(file == null)
                 .BecauseOf(because, reasonArgs)
-                .FailWith("File {0} should not be found in directory {1}.", expectedFile, _dirInfo.FullName);
+                .FailWith(String.Format("File {0} should not be found in directory {1}.", expectedFile, _dirInfo.FullName));
             return new AndConstraint<DirectoryInfoAssertions>(this);
         }
 
@@ -109,8 +109,8 @@ public AndConstraint<DirectoryInfoAssertions> HaveFilesMatching(
             Execute.Assertion
                 .ForCondition(matchingFileExists == true)
                 .BecauseOf(because, reasonArgs)
-                .FailWith("Expected directory {0} to contain files matching {1}, but no matching file exists.",
-                    _dirInfo.FullName, expectedFilesSearchPattern);
+                .FailWith(String.Format("Expected directory {0} to contain files matching {1}, but no matching file exists.",
+                    _dirInfo.FullName, expectedFilesSearchPattern));
 
             return new AndConstraint<DirectoryInfoAssertions>(this);
         }
@@ -132,8 +132,8 @@ public AndConstraint<DirectoryInfoAssertions> NotHaveFilesMatching(string expect
         {
             var matchingFileCount = _dirInfo.EnumerateFiles(expectedFilesSearchPattern, searchOption).Count();
             Execute.Assertion.ForCondition(matchingFileCount == 0)
-                .FailWith("Found {0} files that should not exist in directory {1}. No file matching {2} should exist.",
-                    matchingFileCount, _dirInfo.FullName, expectedFilesSearchPattern);
+                .FailWith(String.Format("Found {0} files that should not exist in directory {1}. No file matching {2} should exist.",
+                    matchingFileCount, _dirInfo.FullName, expectedFilesSearchPattern));
             return new AndConstraint<DirectoryInfoAssertions>(this);
         }
 
@@ -141,7 +141,7 @@ public AndConstraint<DirectoryInfoAssertions> HaveDirectory(string expectedDir)
         {
             var dir = _dirInfo.EnumerateDirectories(expectedDir, SearchOption.TopDirectoryOnly).SingleOrDefault();
             Execute.Assertion.ForCondition(dir != null)
-                .FailWith("Expected directory {0} cannot be found inside directory {1}.", expectedDir, _dirInfo.FullName);
+                .FailWith(String.Format("Expected directory {0} cannot be found inside directory {1}.", expectedDir, _dirInfo.FullName));
 
             return new AndConstraint<DirectoryInfoAssertions>(new DirectoryInfoAssertions(dir));
         }
@@ -160,7 +160,7 @@ public AndConstraint<DirectoryInfoAssertions> NotHaveDirectory(string unexpected
         {
             var dir = _dirInfo.EnumerateDirectories(unexpectedDir, SearchOption.TopDirectoryOnly).SingleOrDefault();
             Execute.Assertion.ForCondition(dir == null)
-                .FailWith("Directory {0} should not be found in directory {1}.", unexpectedDir, _dirInfo.FullName);
+                .FailWith(String.Format("Directory {0} should not be found in directory {1}.", unexpectedDir, _dirInfo.FullName));
 
             return new AndConstraint<DirectoryInfoAssertions>(new DirectoryInfoAssertions(dir));
         }
diff --git a/test/Microsoft.DotNet.Tools.Tests.Utilities/Microsoft.DotNet.Tools.Tests.Utilities.csproj b/test/Microsoft.DotNet.Tools.Tests.Utilities/Microsoft.DotNet.Tools.Tests.Utilities.csproj
index 27da1cfb8f57..485ec5fad717 100644
--- a/test/Microsoft.DotNet.Tools.Tests.Utilities/Microsoft.DotNet.Tools.Tests.Utilities.csproj
+++ b/test/Microsoft.DotNet.Tools.Tests.Utilities/Microsoft.DotNet.Tools.Tests.Utilities.csproj
@@ -4,7 +4,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="4.18.0" />
+    <PackageReference Include="FluentAssertions" Version="6.12.0" />
     <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="Microsoft.DotNet.Cli.Utils" Version="$(MicrosoftDotNetCliUtilsPackageVersion)" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
diff --git a/test/core-sdk-tasks.Tests/core-sdk-tasks.Tests.csproj b/test/core-sdk-tasks.Tests/core-sdk-tasks.Tests.csproj
index 47b6ce51724b..0e751c8abc19 100644
--- a/test/core-sdk-tasks.Tests/core-sdk-tasks.Tests.csproj
+++ b/test/core-sdk-tasks.Tests/core-sdk-tasks.Tests.csproj
@@ -5,7 +5,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="FluentAssertions" Version="4.18.0" />
+    <PackageReference Include="FluentAssertions" Version="6.12.0" />
   </ItemGroup>
 
   <ItemGroup>