[spec] set .NET 8 tests only for linux

Author: i4004

.github/workflows/build.yml

@@ -20,6 +20,10 @@ jobs:
           - os: ubuntu-latest
             solution: Simplify.NetCore.sln
             tests-exclude-category: Windows
+            dotnet-test-framework: net8.0
+
+    env:
+      DOTNET_TEST_FRAMEWORK: ${{ matrix.dotnet-test-framework }} # Set at job level
 
     steps:
       - name: Code Checkout
@@ -35,7 +39,7 @@ jobs:
         run: dotnet build ${{ matrix.solution }} --no-restore -c Release
 
       - name: Perform Unit Testing
-        run: dotnet test ${{ matrix.solution }} --no-build -c Release --framework net8.0 --filter "TestCategory != Integration & TestCategory != ${{ matrix.tests-exclude-category }}" --verbosity normal
+        run: dotnet test ${{ matrix.solution }} --no-build -c Release --filter "TestCategory != Integration & TestCategory != ${{ matrix.tests-exclude-category }}" --verbosity normal
 
       - name: Create Packages
         run: dotnet pack ${{ matrix.solution }} --no-build -c Release -o ./publish