Try out last preview

Directory.Packages.props

@@ -56,7 +56,7 @@
     <PackageVersion Include="ModernWpfUI" Version="0.9.4" />
     <!-- Moq to stay below v4.20 due to behavior change. need to be sure fixed -->
     <PackageVersion Include="Moq" Version="4.18.4" />
-    <PackageVersion Include="MSTest" Version="3.8.2" />
+    <PackageVersion Include="MSTest" Version="3.9.0-preview.25124.5" />
     <PackageVersion Include="NLog" Version="5.0.4" />
     <PackageVersion Include="NLog.Extensions.Logging" Version="5.3.8" />
     <PackageVersion Include="NLog.Schema" Version="5.2.8" />

nuget.config

@@ -3,10 +3,17 @@
 	<packageSources>
 		<clear />
 		<add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+		<!-- TEMPORARY ONLY FOR TESTING PREVIEW IN PR - DON'T MERGE! -->
+		<add key="test-tools" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/test-tools/nuget/v3/index.json" />
 	</packageSources>
 	<packageSourceMapping>
 		<packageSource key="nuget.org">
 			<package pattern="*" />
 		</packageSource>
+		<packageSource key="test-tools">
+			<package pattern="MSTest" />
+			<package pattern="MSTest.*" />
+			<package pattern="Microsoft.Testing.*" />
+		</packageSource>
 	</packageSourceMapping>
 </configuration>