Unify test execution steps

Turns out xunit _can_ run tests on Mono, you just have to install
an additional package to work around a vstest bug.

See microsoft/vstest#2469

.github/workflows/build.yml

@@ -49,32 +49,14 @@ jobs:
     - name: Test
       run: dotnet test --no-build -c ${{ matrix.config }}
 
-    - name: Test (Windows)
-      if: startsWith (matrix.os, 'windows')
-      run: dotnet test -c ${{ matrix.config }} --no-build
 #      run: dotnet test -c ${{ matrix.config }} --no-build --blame-hang-timeout 5m --diag TestResults-${{ matrix.config }}-${{ matrix.os }}/Log/test_log.txt --logger trx --results-directory TestResults-${{ matrix.config }}-${{ matrix.os }}
-
 #    - name: Test diagnostics
 #      if: failure() && startsWith (matrix.os, 'windows')
 #      uses: actions/upload-artifact@v2
 #      with:
 #        name: test-results-${{ matrix.config }}-${{ matrix.os }}
 #        path: TestResults-${{ matrix.config }}-${{ matrix.os }}
 
-      # dotnet test doesn't support mono so we have to use the xunit console runner
-    - name: Set up NuGet
-      if: startsWith (matrix.os, 'windows') == false
-      uses: nuget/setup-nuget@v1
-
-    - name: Test (Linux/Mac)
-      if: startsWith (matrix.os, 'windows') == false
-      run: |
-        nuget install xunit.runner.console -Version 2.4.2 -OutputDirectory testrunner
-        mono ./testrunner/xunit.runner.console.2.4.2/tools/net472/xunit.console.exe ./Mono.TextTemplating.Tests/bin/${{ matrix.config }}/net472/Mono.TextTemplating.Tests.dll -parallel none -noshadow
-        dotnet test -c ${{ matrix.config }} --no-build -f netcoreapp2.1
-        dotnet test -c ${{ matrix.config }} --no-build -f netcoreapp3.1
-        dotnet test -c ${{ matrix.config }} --no-build -f net5.0
-
     - uses: actions/upload-artifact@v3
       if: matrix.config == 'Release' && startsWith(matrix.os, 'windows')
       with:

Mono.TextTemplating.Tests/Mono.TextTemplating.Tests.csproj

@@ -7,17 +7,24 @@
     <DefineConstants Condition="'$(TargetFramework)'=='net472'">$(DefineConstants);FEATURE_APPDOMAINS</DefineConstants>
     <DefaultItemExcludes>$(DefaultItemExcludes);TestCases\**</DefaultItemExcludes>
   </PropertyGroup>
+
   <ItemGroup>
     <ProjectReference Include="..\Mono.TextTemplating\Mono.TextTemplating.csproj" />
     <ProjectReference Include="..\Mono.TextTemplating.Roslyn\Mono.TextTemplating.Roslyn.csproj" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
-    <PackageReference Include="xunit" Version="2.4.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
     <!-- fix conflicts in indirect references -->
     <PackageReference Include="System.Collections.Immutable" Version="5.0.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.Win32.Registry" Version="5.0.0" PrivateAssets="all" />
   </ItemGroup>
 
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
+    <PackageReference Include="xunit" Version="2.4.2" />
+    <!-- newer versions drop netcoreapp2.1 -->
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />
+    <!-- seems to be required for tests to run on Mono -->
+    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="17.3.2" Condition="'$(TargetFramework)'=='net472' And $([MSBuild]::IsOSUnixLike())" />
+  </ItemGroup>
+
   <ItemGroup>
     <None Include="TestCases\**\*.*" CopyToOutputDirectory="PreserveNewest" />
     <!-- disable parallel test execution on github actions, it hangs the runner there -->