build: InternalsVisibleTo excluded from test projects

src/Directory.Build.props

@@ -19,11 +19,12 @@
     </AllowedReferenceRelatedFileExtensions>
   </PropertyGroup>
 
-  <ItemGroup>
-    <AssemblyAttribute Include="System.Runtime.CompilerServices.InternalsVisibleToAttribute">
-      <_Parameter1>$(AssemblyName).Tests</_Parameter1>
-    </AssemblyAttribute>
+  <!-- For only NON-TEST projects -->
+  <ItemGroup Condition="!$(ProjectName.EndsWith('.Tests'))">
+    <InternalsVisibleTo Include="$(AssemblyName).Tests" />
+  </ItemGroup>
 
+  <ItemGroup>
     <!-- From https://github.com/dotnet/msbuild/pull/6285 -->
     <AssemblyAttribute Include="System.CLSCompliantAttribute">
       <_Parameter1>false</_Parameter1>