Update tests to cover .net8

Author: TonyTroeff

.github/workflows/pull-request-validation.yml

@@ -20,7 +20,9 @@ jobs:
     - name: Setup .NET
       uses: actions/setup-dotnet@v4
       with:
-        dotnet-version: 9.x
+        dotnet-version: |
+          8.x
+          9.x
 
     - name: Restore dependencies
       run: dotnet restore ./src/OneBitSoftware.Utilities.OperationResult.sln
@@ -29,4 +31,4 @@ jobs:
       run: dotnet build ./src/OneBitSoftware.Utilities.OperationResult.sln --no-restore --configuration "${{ env.CONFIGURATION }}"
 
     - name: Test
-      run: dotnet test ./src/OneBitSoftware.Utilities.OperationResult.sln --no-build --verbosity normal
+      run: dotnet test ./src/OneBitSoftware.Utilities.OperationResult.sln --no-build --configuration "${{ env.CONFIGURATION }}" --verbosity normal

tests/OneBitSoftware.Utilities.OperationResultTests/OneBitSoftware.Utilities.OperationResultTests.csproj

@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
-    <TargetFramework>net9.0</TargetFramework>
+    <TargetFramework>net8.0;net9.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
   </PropertyGroup>