[unit-test] Fix "No test is available" for netcoreapp3.1 target framework.

Restores unit-test execution for EOL/out-of-support target frameworks

Author: albertospelta

src/Dax.Metadata.Tests/Dax.Metadata.Tests.csproj

@@ -1,8 +1,10 @@
 <Project Sdk="Microsoft.NET.Sdk">
-
+  
   <PropertyGroup>
     <TargetFrameworks>net462;netcoreapp3.1;net6.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
+    <!-- It's ok if a test target has exited support. Disable NETSSDK1138 warning -->
+    <CheckEolTargetFramework>false</CheckEolTargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

src/Dax.Model.Extractor.Tests/Dax.Model.Extractor.Tests.csproj

@@ -3,6 +3,8 @@
   <PropertyGroup>
     <TargetFrameworks>net462;netcoreapp3.1;net6.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
+    <!-- It's ok if a test target has exited support. Disable NETSSDK1138 warning -->
+    <CheckEolTargetFramework>false</CheckEolTargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

src/Dax.Vpax.Tests/Dax.Vpax.Tests.csproj

@@ -3,6 +3,8 @@
   <PropertyGroup>
     <TargetFrameworks>net462;netcoreapp3.1;net6.0</TargetFrameworks>
     <IsPackable>false</IsPackable>
+    <!-- It's ok if a test target has exited support. Disable NETSSDK1138 warning -->
+    <CheckEolTargetFramework>false</CheckEolTargetFramework>
   </PropertyGroup>
 
   <ItemGroup>

src/Directory.Packages.props

@@ -14,9 +14,10 @@
     <PackageVersion Include="Newtonsoft.Json" Version="13.0.3" />
     <PackageVersion Include="System.Data.OleDb" Version="6.0.0" />
     <PackageVersion Include="System.IO.Packaging" Version="6.0.0" />
-    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.7.1" />
-    <PackageVersion Include="coverlet.collector" Version="6.0.0" />
-    <PackageVersion Include="xunit" Version="2.5.0" />
-    <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.0" />
+    <!-- pinned dependencies required to test out-of-support target frameworks -->
+    <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="[16.3.0]" />
+    <PackageVersion Include="coverlet.collector" Version="[6.0.0]" />
+    <PackageVersion Include="xunit" Version="[2.3.1]" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="[2.3.1]" />
   </ItemGroup>
 </Project>