diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index d3a3684..f9baa81 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -24,7 +24,9 @@ jobs:
     - name: Setup dotnet
       uses: actions/setup-dotnet@v5.2.0
       with:
-        dotnet-version: 8.0.x
+        dotnet-version: | 
+          8.0.x
+          3.1.426
     - name: Checkout code
       uses: actions/checkout@v5
     - name: Cache SonarQube Cloud packages
@@ -51,8 +53,12 @@ jobs:
       run: ${{ runner.temp }}\scanner\dotnet-sonarscanner begin /k:"KxSystems_csharpkdb" /o:"kxsystems" /d:sonar.token="$env:SONAR_TOKEN" /d:sonar.cs.vstest.reportsPaths="**\TestResults\*.trx" /d:sonar.cs.opencover.reportsPaths="*\coverage.opencover.xml" /d:sonar.verbose=false
     - name: Build 
       run : dotnet build /p:Configuration=Release .\CSharpKdb.sln
-    - name: Test
-      run: dotnet test /p:Configuration=Release --no-build .\kx.Test\kx.Test.csproj --logger:trx /p:CollectCoverage=true /p:CoverletOutputFormat=opencover
+    - name: Test .NET Framework 4.7.2
+      run: dotnet test .\kx.Test\kx.Test.csproj -c Release -f net472 --no-build --logger:trx
+    - name: Test .NET Core 3.1
+      run: dotnet test .\kx.Test\kx.Test.csproj -c Release -f netcoreapp3.1 --no-build --logger:trx
+    - name: Test .NET 8
+      run: dotnet test .\kx.Test\kx.Test.csproj -c Release -f net8.0 --no-build --logger:trx /p:CollectCoverage=true /p:CoverletOutputFormat=opencover
     - name: SonarQube Cloud scanner finish
       if: ${{ github.event_name == 'push' || (github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository && env.SONAR_TOKEN != '') }} 
       run: ${{ runner.temp }}\scanner\dotnet-sonarscanner end /d:sonar.token="$env:SONAR_TOKEN"
diff --git a/kx.Test/kx.Test.csproj b/kx.Test/kx.Test.csproj
index 0892da4..3598a62 100644
--- a/kx.Test/kx.Test.csproj
+++ b/kx.Test/kx.Test.csproj
@@ -1,7 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net8.0</TargetFramework>
+    <!-- net472 for netstandard2.0, netcoreapp3.1 for netstandard2.1, net8.0 for net8.0 -->
+    <TargetFrameworks>net472;netcoreapp3.1;net8.0</TargetFrameworks>
 
     <IsPackable>false</IsPackable>