xUnit: remove defunct helpers, add deterministic init via assembly fixture

tests/FSharp.Compiler.ComponentTests/FSharp.Compiler.ComponentTests.fsproj

@@ -380,6 +380,7 @@
     <Compile Include="TypeChecks\Graph\Scenarios.fs" />
     <Compile Include="TypeChecks\Graph\DependencyResolutionTests.fs" />
     <Compile Include="TypeChecks\Graph\CompilationTests.fs" />
+    <Content Include="testconfig.json" />
     <Content Include="TypeChecks\Graph\scrape.fsx" CopyToOutputDirectory="Never" />
     <Compile Include="TypeChecks\Graph\CompilationFromCmdlineArgsTests.fs" />
     <Compile Include="TypeChecks\Graph\TypedTreeGraph.fs" />
@@ -484,6 +485,13 @@
     </None>
   </ItemGroup>
 
+  <!-- xUnit3 configuration for this test project (MTP mode) -->
+  <ItemGroup>
+    <Content Include="testconfig.json">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
+  </ItemGroup>
+
   <ItemGroup>
     <Content Include="resources\**" CopyToOutputDirectory="Never" CopyToPublishDirectory="PreserveNewest" />
     <EmbeddedResource Remove="Properties\**" />

tests/FSharp.Compiler.ComponentTests/testconfig.json

@@ -0,0 +1,5 @@
+{
+  "xUnit": {
+    "maxParallelThreads": "0.5x"
+  }
+}

tests/FSharp.Test.Utilities/FSharp.Test.Utilities.fsproj

@@ -42,7 +42,6 @@
     <Compile Include="FileInlineDataAttribute.fs" />
     <Compile Include="ReflectionHelper.fs" />
     <Compile Include="SurfaceArea.fs" />
-    <Compile Include="XunitHelpers.fs" />
     <Compile Include="XunitSetup.fs" />
   </ItemGroup>
 
@@ -104,7 +103,7 @@
  <!-- 44: AssemblyName.CodeBase is deprecated but needed for assembly resolution in VS integration tests -->
 </PropertyGroup>
   <ItemGroup>
-    <PackageReference Include="System.Collections.Immutable" Version="$(SystemCollectionsImmutableVersion)" GeneratePathProperty="true"  />
+    <PackageReference Include="System.Collections.Immutable" Version="$(SystemCollectionsImmutableVersion)" GeneratePathProperty="true" />
     <PackageReference Include="Microsoft.CodeAnalysis.Workspaces.Common" Version="$(RoslynForTestingButNotForVSLayer)" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="$(RoslynForTestingButNotForVSLayer)" />
     <PackageReference Include="Microsoft.CodeAnalysis.Test.Resources.Proprietary" Version="$(MicrosoftCodeAnalysisTestResourcesProprietaryVersion)" />

tests/FSharp.Test.Utilities/XunitSetup.fs

@@ -1,40 +1,40 @@
 namespace FSharp.Test
 
+open System
 open Xunit
+open TestFramework
 
-// xUnit3 assembly fixtures: ensure TestConsole is installed once per assembly
-// This replaces the OneTimeSetup.EnsureInitialized() call that was done in FSharpXunitFramework
-module private XUnitInit =
-    let private ensureInitialized = lazy (
+/// xUnit3 assembly fixture: performs one-time setup for the test assembly.
+/// Registered via [<assembly: AssemblyFixture(typeof<FSharpTestAssemblyFixture>)>] below.
+/// The constructor is called by xUnit once before any tests in the assembly run.
+type FSharpTestAssemblyFixture() =
+    do
 #if !NETCOREAPP
-        // On .NET Framework, we need the assembly resolver for finding assemblies
-        // that might be in different locations (e.g., when FSI loads assemblies)
+        // We need AssemblyResolver already here, because OpenTelemetry loads some assemblies dynamically.
+        log "Adding AssemblyResolver"
         AssemblyResolver.addResolver()
 #endif
+        log $"Server GC enabled: {Runtime.GCSettings.IsServerGC}"
+        log "Installing TestConsole redirection"
         TestConsole.install()
-    )
-
-    /// Call this to ensure TestConsole is installed. Safe to call multiple times.
-    let initialize() = ensureInitialized.Force()
+        logConfig initialConfig
 
 /// Exclude from parallelization. Execute test cases in sequence and do not run any other collections at the same time.
 /// see https://github.com/xunit/xunit/issues/1999#issuecomment-522635397
 [<CollectionDefinition(nameof NotThreadSafeResourceCollection, DisableParallelization = true)>]
 type NotThreadSafeResourceCollection() = class end
 
+/// Mark test cases as not safe to run in parallel with other test cases of the same test collection.
+/// In case Xunit 3 enables internal parallelization of test collections.
+[<AttributeUsage(AttributeTargets.Class ||| AttributeTargets.Method, AllowMultiple = false)>]
+type RunTestCasesInSequenceAttribute() = inherit Attribute()
+
 module XUnitSetup =
 
-    // NOTE: Custom TestFramework temporarily disabled due to xUnit3 API incompatibilities
-    // TODO: Reimplement FSharpXunitFramework for xUnit3 if needed
-    // [<assembly: TestFramework("FSharp.Test.FSharpXunitFramework", "FSharp.Test.Utilities")>]
-
     // NOTE: CaptureTrace is disabled because it conflicts with TestConsole.ExecutionCapture
     // which is used by FSI tests to capture console output. xUnit3's trace capture intercepts
     // console output before it can reach TestConsole's redirectors.
     // [<assembly: CaptureTrace>]
-
-    /// Call this to ensure TestConsole is installed. Safe to call multiple times.
-    let initialize() = XUnitInit.initialize()
-
-    // Force initialization when module is loaded
-    do initialize()
+
+    [<assembly: AssemblyFixture(typeof<FSharpTestAssemblyFixture>)>]
+    do ()

tests/fsharp/FSharpSuite.Tests.fsproj

@@ -97,13 +97,6 @@
     <EmbeddedResource Remove="**" />
   </ItemGroup>
 
-  <!-- xUnit3 configuration for this test project (MTP mode) -->
-  <ItemGroup>
-    <Content Include="testconfig.json">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </Content>
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="$(FSharpSourcesRoot)\FSharp.Build\FSharp.Build.fsproj" />
     <ProjectReference Include="$(FSharpSourcesRoot)\Compiler\FSharp.Compiler.Service.fsproj" />