Update headless xUnit support to v3 (#20481)

* Update headless xUnit support to v3

* Update API suppressions

api/Avalonia.Headless.XUnit.nupkg.xml

@@ -0,0 +1,76 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- https://learn.microsoft.com/dotnet/fundamentals/package-validation/diagnostic-ids -->
+<Suppressions xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTestFrameworkTypeDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaUIFactDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTestFrameworkTypeDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaUIFactDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Headless.XUnit.AvaloniaFactAttribute.#ctor</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Headless.XUnit.AvaloniaTheoryDiscoverer.#ctor(Xunit.Abstractions.IMessageSink)</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Headless.XUnit.AvaloniaFactAttribute.#ctor</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0002</DiagnosticId>
+    <Target>M:Avalonia.Headless.XUnit.AvaloniaTheoryDiscoverer.#ctor(Xunit.Abstractions.IMessageSink)</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0007</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTheoryDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0007</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTheoryDiscoverer</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0008</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTestFrameworkAttribute</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net10.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0008</DiagnosticId>
+    <Target>T:Avalonia.Headless.XUnit.AvaloniaTestFrameworkAttribute</Target>
+    <Left>baseline/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Left>
+    <Right>current/Avalonia.Headless.XUnit/lib/net8.0/Avalonia.Headless.XUnit.dll</Right>
+  </Suppression>
+</Suppressions>

build/XUnit.props

@@ -1,14 +1,13 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
-  <ItemGroup Condition="'$(IsXUnit2)'!='true'">
+
+  <ItemGroup>
     <PackageReference Include="xunit.v3.mtp-v2" Version="3.2.1" />
   </ItemGroup>
-  <ItemGroup Condition="'$(IsXUnit2)'=='true'">
+
-    <PackageReference Include="xunit" Version="2.9.3" />
-    <PackageReference Include="YTest.MTP.XUnit2" Version="1.0.2" />
-  </ItemGroup>
   <PropertyGroup>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)\avalonia.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>False</SignAssembly>
     <NoWarn>$(NoWarn);CS8002</NoWarn> <!-- ignore signing warnings for unit tests -->
   </PropertyGroup>
+
 </Project>

src/Headless/Avalonia.Headless.XUnit/Avalonia.Headless.XUnit.csproj

@@ -5,8 +5,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <!-- Use lower minor version, as it is supposed to be compatible  -->
+    <PackageReference Include="xunit.v3.extensibility.core" Version="3.2.1" />
-    <PackageReference Include="xunit.core" Version="2.4.0" />
   </ItemGroup>
 
   <ItemGroup>

src/Headless/Avalonia.Headless.XUnit/AvaloniaDelayEnumeratedTheoryTestCase.cs

@@ -0,0 +1,80 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Threading;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaDelayEnumeratedTheoryTestCase
+    : XunitDelayEnumeratedTheoryTestCase, ISelfExecutingXunitTestCase
+{
+    public AvaloniaDelayEnumeratedTheoryTestCase(
+        IXunitTestMethod testMethod,
+        string testCaseDisplayName,
+        string uniqueID,
+        bool @explicit,
+        bool skipTestWithoutData,
+        Type[]? skipExceptions = null,
+        string? skipReason = null,
+        Type? skipType = null,
+        string? skipUnless = null,
+        string? skipWhen = null,
+        Dictionary<string, HashSet<string>>? traits = null,
+        string? sourceFilePath = null,
+        int? sourceLineNumber = null,
+        int? timeout = null)
+        : base(
+            testMethod,
+            testCaseDisplayName,
+            uniqueID,
+            @explicit,
+            skipTestWithoutData,
+            skipExceptions,
+            skipReason,
+            skipType,
+            skipUnless,
+            skipWhen,
+            traits,
+            sourceFilePath,
+            sourceLineNumber,
+            timeout)
+    {
+    }
+
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    [Obsolete("Called by the de-serializer; should only be called by deriving classes for de-serialization purposes")]
+    public AvaloniaDelayEnumeratedTheoryTestCase()
+    {
+    }
+
+    public async ValueTask<RunSummary> Run(
+        ExplicitOption explicitOption,
+        IMessageBus messageBus,
+        object?[] constructorArguments,
+        ExceptionAggregator aggregator,
+        CancellationTokenSource cancellationTokenSource)
+    {
+        var tests = await aggregator.RunAsync(CreateTests, []);
+
+        // We need to block the XUnit thread to ensure its concurrency throttle is effective.
+        // See https://github.com/AArnott/Xunit.StaFact/pull/55#issuecomment-826187354 for details.
+        var runSummary = Task.Run(async () => await AvaloniaTestCaseRunner.Instance.Run(
+                this,
+                tests,
+                messageBus,
+                aggregator,
+                cancellationTokenSource,
+                TestCaseDisplayName,
+                SkipReason,
+                explicitOption,
+                constructorArguments))
+            .GetAwaiter()
+            .GetResult();
+
+        return runSummary;
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaFact.cs

@@ -1,9 +1,7 @@
 using System;
-using System.ComponentModel;
+using System.Runtime.CompilerServices;
-using System.Threading;
 using Xunit;
-using Xunit.Abstractions;
+using Xunit.v3;
-using Xunit.Sdk;
 
 namespace Avalonia.Headless.XUnit;
 
@@ -12,24 +10,8 @@ namespace Avalonia.Headless.XUnit;
 /// such that awaited expressions resume on the test's "main thread".
 /// </summary>
 [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
-[XunitTestCaseDiscoverer("Avalonia.Headless.XUnit.AvaloniaUIFactDiscoverer", "Avalonia.Headless.XUnit")]
+[XunitTestCaseDiscoverer(typeof(AvaloniaFactDiscoverer))]
-public sealed class AvaloniaFactAttribute : FactAttribute
+public sealed class AvaloniaFactAttribute(
-{
+    [CallerFilePath] string? sourceFilePath = null,
-    
+    [CallerLineNumber] int sourceLineNumber = -1)
-}
+    : FactAttribute(sourceFilePath, sourceLineNumber);
-
-[EditorBrowsable(EditorBrowsableState.Never)]
-public class AvaloniaUIFactDiscoverer : FactDiscoverer
-{
-    private readonly IMessageSink diagnosticMessageSink;
-    public AvaloniaUIFactDiscoverer(IMessageSink diagnosticMessageSink)
-        : base(diagnosticMessageSink)
-    {
-        this.diagnosticMessageSink = diagnosticMessageSink;
-    }
-
-    protected override IXunitTestCase CreateTestCase(ITestFrameworkDiscoveryOptions discoveryOptions, ITestMethod testMethod, IAttributeInfo factAttribute)
-    {
-        return new AvaloniaTestCase(diagnosticMessageSink, discoveryOptions.MethodDisplayOrDefault(), testMethod);
-    }
-}

src/Headless/Avalonia.Headless.XUnit/AvaloniaFactDiscoverer.cs

@@ -0,0 +1,34 @@
+using System;
+using System.ComponentModel;
+using Xunit.Internal;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+[EditorBrowsable(EditorBrowsableState.Never)]
+public class AvaloniaFactDiscoverer : FactDiscoverer
+{
+    protected override IXunitTestCase CreateTestCase(
+        ITestFrameworkDiscoveryOptions discoveryOptions,
+        IXunitTestMethod testMethod,
+        IFactAttribute factAttribute)
+    {
+        var details = TestIntrospectionHelper.GetTestCaseDetails(discoveryOptions, testMethod, factAttribute);
+
+        return new AvaloniaTestCase(
+            details.ResolvedTestMethod,
+            details.TestCaseDisplayName,
+            details.UniqueID,
+            details.Explicit,
+            details.SkipExceptions,
+            details.SkipReason,
+            details.SkipType,
+            details.SkipUnless,
+            details.SkipWhen,
+            testMethod.Traits.ToReadWrite(StringComparer.OrdinalIgnoreCase),
+            sourceFilePath: details.SourceFilePath,
+            sourceLineNumber: details.SourceLineNumber,
+            timeout: details.Timeout);
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestAssemblyRunner.cs

@@ -1,126 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Reflection;
-using System.Threading;
-using System.Threading.Tasks;
-using Avalonia.Threading;
-using Xunit.Abstractions;
-using Xunit.Sdk;
-
-namespace Avalonia.Headless.XUnit;
-
-internal class AvaloniaTestAssemblyRunner : XunitTestAssemblyRunner
-{
-    private HeadlessUnitTestSession? _session;
-
-    public AvaloniaTestAssemblyRunner(ITestAssembly testAssembly, IEnumerable<IXunitTestCase> testCases,
-        IMessageSink diagnosticMessageSink, IMessageSink executionMessageSink,
-        ITestFrameworkExecutionOptions executionOptions) : base(testAssembly, testCases, diagnosticMessageSink,
-        executionMessageSink, executionOptions)
-    {
-    }
-
-    protected override void SetupSyncContext(int maxParallelThreads)
-    {
-        _session = HeadlessUnitTestSession.GetOrStartForAssembly(
-            Assembly.Load(new AssemblyName(TestAssembly.Assembly.Name)));
-        base.SetupSyncContext(1);
-    }
-
-    public override void Dispose()
-    {
-        _session?.Dispose();
-        base.Dispose();
-    }
-
-    protected override Task<RunSummary> RunTestCollectionAsync(
-        IMessageBus messageBus,
-        ITestCollection testCollection,
-        IEnumerable<IXunitTestCase> testCases,
-        CancellationTokenSource cancellationTokenSource)
-    {
-        return new AvaloniaTestCollectionRunner(_session!, testCollection, testCases, DiagnosticMessageSink, messageBus,
-            TestCaseOrderer, new ExceptionAggregator(Aggregator), cancellationTokenSource).RunAsync();
-    }
-
-    private class AvaloniaTestCollectionRunner : XunitTestCollectionRunner
-    {
-        private readonly HeadlessUnitTestSession _session;
-
-        public AvaloniaTestCollectionRunner(HeadlessUnitTestSession session,
-            ITestCollection testCollection, IEnumerable<IXunitTestCase> testCases,
-            IMessageSink diagnosticMessageSink, IMessageBus messageBus, ITestCaseOrderer testCaseOrderer,
-            ExceptionAggregator aggregator, CancellationTokenSource cancellationTokenSource) : base(testCollection,
-            testCases, diagnosticMessageSink, messageBus, testCaseOrderer, aggregator, cancellationTokenSource)
-        {
-            _session = session;
-        }
-
-        protected override Task<RunSummary> RunTestClassAsync(
-            ITestClass testClass,
-            IReflectionTypeInfo @class,
-            IEnumerable<IXunitTestCase> testCases)
-        {
-            return new AvaloniaTestClassRunner(_session, testClass, @class, testCases, DiagnosticMessageSink, MessageBus,
-                TestCaseOrderer, new ExceptionAggregator(Aggregator), CancellationTokenSource,
-                CollectionFixtureMappings).RunAsync();
-        }
-    }
-
-    private class AvaloniaTestClassRunner : XunitTestClassRunner
-    {
-        private readonly HeadlessUnitTestSession _session;
-
-        public AvaloniaTestClassRunner(HeadlessUnitTestSession session, ITestClass testClass,
-            IReflectionTypeInfo @class,
-            IEnumerable<IXunitTestCase> testCases, IMessageSink diagnosticMessageSink, IMessageBus messageBus,
-            ITestCaseOrderer testCaseOrderer, ExceptionAggregator aggregator,
-            CancellationTokenSource cancellationTokenSource, IDictionary<Type, object> collectionFixtureMappings) :
-            base(testClass, @class, testCases, diagnosticMessageSink, messageBus, testCaseOrderer, aggregator,
-                cancellationTokenSource, collectionFixtureMappings)
-        {
-            _session = session;
-        }
-
-        protected override Task<RunSummary> RunTestMethodAsync(
-            ITestMethod testMethod,
-            IReflectionMethodInfo method,
-            IEnumerable<IXunitTestCase> testCases,
-            object[] constructorArguments)
-        {
-            return new AvaloniaTestMethodRunner(_session, testMethod, Class, method, testCases, DiagnosticMessageSink,
-                MessageBus, new ExceptionAggregator(Aggregator), CancellationTokenSource,
-                constructorArguments).RunAsync();
-        }
-    }
-
-    private class AvaloniaTestMethodRunner : XunitTestMethodRunner
-    {
-        private readonly HeadlessUnitTestSession _session;
-        private readonly IMessageBus _messageBus;
-        private readonly ExceptionAggregator _aggregator;
-        private readonly CancellationTokenSource _cancellationTokenSource;
-        private readonly object[] _constructorArguments;
-
-        public AvaloniaTestMethodRunner(HeadlessUnitTestSession session, ITestMethod testMethod,
-            IReflectionTypeInfo @class,
-            IReflectionMethodInfo method, IEnumerable<IXunitTestCase> testCases, IMessageSink diagnosticMessageSink,
-            IMessageBus messageBus, ExceptionAggregator aggregator, CancellationTokenSource cancellationTokenSource,
-            object[] constructorArguments) : base(testMethod, @class, method, testCases, diagnosticMessageSink,
-            messageBus, aggregator, cancellationTokenSource, constructorArguments)
-        {
-            _session = session;
-            _messageBus = messageBus;
-            _aggregator = aggregator;
-            _cancellationTokenSource = cancellationTokenSource;
-            _constructorArguments = constructorArguments;
-        }
-
-        protected override Task<RunSummary> RunTestCaseAsync(IXunitTestCase testCase)
-        {
-            return AvaloniaTestCaseRunner.RunTest(_session, testCase, testCase.DisplayName, testCase.SkipReason,
-                _constructorArguments, testCase.TestMethodArguments, _messageBus, _aggregator,
-                _cancellationTokenSource);
-        }
-    }
-}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestCase.cs

@@ -1,20 +1,46 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel;
 using System.Threading;
 using System.Threading.Tasks;
-using Xunit.Abstractions;
+using Avalonia.Threading;
 using Xunit.Sdk;
+using Xunit.v3;
 
 namespace Avalonia.Headless.XUnit;
 
-internal class AvaloniaTestCase : XunitTestCase
+internal sealed class AvaloniaTestCase : XunitTestCase, ISelfExecutingXunitTestCase
 {
     public AvaloniaTestCase(
-        IMessageSink diagnosticMessageSink,
+        IXunitTestMethod testMethod,
-        TestMethodDisplay defaultMethodDisplay,
+        string testCaseDisplayName,
-        ITestMethod testMethod,
+        string uniqueID,
-        object?[]? testMethodArguments = null)
+        bool @explicit,
-        : base(diagnosticMessageSink, defaultMethodDisplay, TestMethodDisplayOptions.None, testMethod, testMethodArguments)
+        Type[]? skipExceptions = null,
+        string? skipReason = null,
+        Type? skipType = null,
+        string? skipUnless = null,
+        string? skipWhen = null,
+        Dictionary<string, HashSet<string>>? traits = null,
+        object?[]? testMethodArguments = null,
+        string? sourceFilePath = null,
+        int? sourceLineNumber = null,
+        int? timeout = null)
+        : base(
+            testMethod,
+            testCaseDisplayName,
+            uniqueID,
+            @explicit,
+            skipExceptions,
+            skipReason,
+            skipType,
+            skipUnless,
+            skipWhen,
+            traits,
+            testMethodArguments,
+            sourceFilePath,
+            sourceLineNumber,
+            timeout)
     {
     }
 
@@ -24,23 +50,30 @@ internal class AvaloniaTestCase : XunitTestCase
     {
     }
 
-    public override Task<RunSummary> RunAsync(
+    public async ValueTask<RunSummary> Run(
-        IMessageSink diagnosticMessageSink,
+        ExplicitOption explicitOption,
         IMessageBus messageBus,
-        object[] constructorArguments,
+        object?[] constructorArguments,
         ExceptionAggregator aggregator,
         CancellationTokenSource cancellationTokenSource)
     {
-        var session = HeadlessUnitTestSession.GetOrStartForAssembly(Method.ToRuntimeMethod().DeclaringType?.Assembly);
+        var tests = await aggregator.RunAsync(CreateTests, []);
 
         // We need to block the XUnit thread to ensure its concurrency throttle is effective.
         // See https://github.com/AArnott/Xunit.StaFact/pull/55#issuecomment-826187354 for details.
-        var runSummary =
+        var runSummary = Task.Run(async () => await AvaloniaTestCaseRunner.Instance.Run(
-            Task.Run(() => AvaloniaTestCaseRunner.RunTest(session, this, DisplayName, SkipReason, constructorArguments,
+                this,
-                TestMethodArguments, messageBus, aggregator, cancellationTokenSource))
+                tests,
+                messageBus,
+                aggregator,
+                cancellationTokenSource,
+                TestCaseDisplayName,
+                SkipReason,
+                explicitOption,
+                constructorArguments))
             .GetAwaiter()
             .GetResult();
 
-        return Task.FromResult(runSummary);
+        return runSummary;
     }
 }

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestCaseRunner.cs

@@ -1,103 +1,59 @@
-using System;
+using System.Collections.Generic;
-using System.Collections.Generic;
-using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
-using Avalonia.Threading;
-using Xunit.Abstractions;
 using Xunit.Sdk;
+using Xunit.v3;
 
 namespace Avalonia.Headless.XUnit;
 
-internal class AvaloniaTestCaseRunner : XunitTestCaseRunner
+internal sealed class AvaloniaTestCaseRunner
+    : XunitTestCaseRunnerBase<AvaloniaTestCaseRunnerContext, IXunitTestCase, IXunitTest>
 {
-    private readonly HeadlessUnitTestSession _session;
+    public static AvaloniaTestCaseRunner Instance { get; } = new();
-    private readonly Action? _onAfterTestInvoked;
 
-    public AvaloniaTestCaseRunner(
+    private AvaloniaTestCaseRunner()
-        HeadlessUnitTestSession session, Action? onAfterTestInvoked,
-        IXunitTestCase testCase, string displayName, string skipReason, object[] constructorArguments,
-        object[] testMethodArguments, IMessageBus messageBus, ExceptionAggregator aggregator,
-        CancellationTokenSource cancellationTokenSource) : base(testCase, displayName, skipReason, constructorArguments,
-        testMethodArguments, messageBus, aggregator, cancellationTokenSource)
     {
-        _session = session;
-        _onAfterTestInvoked = onAfterTestInvoked;
     }
 
-    public static Task<RunSummary> RunTest(HeadlessUnitTestSession session,
+    public async ValueTask<RunSummary> Run(
-        IXunitTestCase testCase, string displayName, string skipReason, object[] constructorArguments,
+        IXunitTestCase testCase,
-        object[] testMethodArguments, IMessageBus messageBus, ExceptionAggregator aggregator,
+        IReadOnlyCollection<IXunitTest> tests,
-        CancellationTokenSource cancellationTokenSource)
+        IMessageBus messageBus,
+        ExceptionAggregator aggregator,
+        CancellationTokenSource cancellationTokenSource,
+        string displayName,
+        string? skipReason,
+        ExplicitOption explicitOption,
+        object?[] constructorArguments)
     {
-        var afterTest = () => Dispatcher.UIThread.RunJobs();
+        var session = HeadlessUnitTestSession.GetOrStartForAssembly(testCase.TestClass.Class.Assembly);
-
+
-        var runner = new AvaloniaTestCaseRunner(session, afterTest, testCase, displayName,
+        await using var ctxt = new AvaloniaTestCaseRunnerContext(
-            skipReason, constructorArguments, testMethodArguments, messageBus, aggregator, cancellationTokenSource);
+            testCase,
-        return runner.RunAsync();
+            tests,
-    }
+            messageBus,
-
+            aggregator,
-    protected override XunitTestRunner CreateTestRunner(ITest test, IMessageBus messageBus, Type testClass,
+            cancellationTokenSource,
-        object[] constructorArguments,
+            displayName,
-        MethodInfo testMethod, object[] testMethodArguments, string skipReason,
+            skipReason,
-        IReadOnlyList<BeforeAfterTestAttribute> beforeAfterAttributes,
+            explicitOption,
-        ExceptionAggregator aggregator, CancellationTokenSource cancellationTokenSource)
+            constructorArguments,
-    {
+            session);
-        return new AvaloniaTestRunner(_session, _onAfterTestInvoked, test, messageBus, testClass, constructorArguments,
+        await ctxt.InitializeAsync();
-            testMethod, testMethodArguments, skipReason, beforeAfterAttributes, aggregator, cancellationTokenSource);
+
-    }
+        return await Run(ctxt);
-
-    private class AvaloniaTestRunner : XunitTestRunner
-    {
-        private readonly HeadlessUnitTestSession _session;
-        private readonly Action? _onAfterTestInvoked;
-
-        public AvaloniaTestRunner(
-            HeadlessUnitTestSession session, Action? onAfterTestInvoked,
-            ITest test, IMessageBus messageBus, Type testClass, object[] constructorArguments, MethodInfo testMethod,
-            object[] testMethodArguments, string skipReason,
-            IReadOnlyList<BeforeAfterTestAttribute> beforeAfterAttributes, ExceptionAggregator aggregator,
-            CancellationTokenSource cancellationTokenSource) : base(test, messageBus, testClass, constructorArguments,
-            testMethod, testMethodArguments, skipReason, beforeAfterAttributes, aggregator, cancellationTokenSource)
-        {
-            _session = session;
-            _onAfterTestInvoked = onAfterTestInvoked;
-        }
-
-        protected override Task<decimal> InvokeTestMethodAsync(ExceptionAggregator aggregator)
-        {
-            return _session.Dispatch(
-                () => new AvaloniaTestInvoker(_onAfterTestInvoked, Test, MessageBus, TestClass,
-                    ConstructorArguments, TestMethod, TestMethodArguments, BeforeAfterAttributes, aggregator,
-                    CancellationTokenSource).RunAsync(),
-                CancellationTokenSource.Token);
-        }
     }
 
-    private class AvaloniaTestInvoker : XunitTestInvoker
+    protected override ValueTask<RunSummary> RunTest(
-    {
+        AvaloniaTestCaseRunnerContext ctxt,
-        private readonly Action? _onAfterTestInvoked;
+        IXunitTest test)
-
+        => AvaloniaTestRunner.Instance.Run(
-        public AvaloniaTestInvoker(
+            test,
-            Action? onAfterTestInvoked,
+            ctxt.MessageBus,
-            ITest test, IMessageBus messageBus, Type testClass, object[] constructorArguments, MethodInfo testMethod,
+            ctxt.ConstructorArguments,
-            object[] testMethodArguments, IReadOnlyList<BeforeAfterTestAttribute> beforeAfterAttributes,
+            ctxt.ExplicitOption,
-            ExceptionAggregator aggregator, CancellationTokenSource cancellationTokenSource) : base(test, messageBus,
+            ctxt.Aggregator.Clone(),
-            testClass, constructorArguments, testMethod, testMethodArguments, beforeAfterAttributes, aggregator,
+            ctxt.CancellationTokenSource,
-            cancellationTokenSource)
+            ctxt.BeforeAfterTestAttributes,
-        {
+            ctxt.Session);
-            _onAfterTestInvoked = onAfterTestInvoked;
-        }
-
-        protected override async Task AfterTestMethodInvokedAsync()
-        {
-            await base.AfterTestMethodInvokedAsync();
-
-            // Only here we can execute random code after the test, where exception will be properly handled by the XUnit.
-            if (_onAfterTestInvoked is not null)
-            {
-                Aggregator.Run(_onAfterTestInvoked);
-            }
-        }
-    }
 }

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestCaseRunnerContext.cs

@@ -0,0 +1,31 @@
+using System.Collections.Generic;
+using System.Threading;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaTestCaseRunnerContext(
+    IXunitTestCase testCase,
+    IReadOnlyCollection<IXunitTest> tests,
+    IMessageBus messageBus,
+    ExceptionAggregator aggregator,
+    CancellationTokenSource cancellationTokenSource,
+    string displayName,
+    string? skipReason,
+    ExplicitOption explicitOption,
+    object?[] constructorArguments,
+    HeadlessUnitTestSession session)
+    : XunitTestCaseRunnerContext(
+        testCase,
+        tests,
+        messageBus,
+        aggregator,
+        cancellationTokenSource,
+        displayName,
+        skipReason,
+        explicitOption,
+        constructorArguments)
+{
+    public HeadlessUnitTestSession Session { get; } = session;
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestFramework.cs

@@ -1,35 +1,13 @@
-using System.Collections.Generic;
+using System.Reflection;
-using System.Reflection;
+using Xunit.v3;
-using Xunit.Abstractions;
-using Xunit.Sdk;
 
 namespace Avalonia.Headless.XUnit;
 
-internal class AvaloniaTestFramework : XunitTestFramework
+internal sealed class AvaloniaTestFramework : XunitTestFramework
 {
-    public AvaloniaTestFramework(IMessageSink messageSink) : base(messageSink)
+    protected override ITestFrameworkDiscoverer CreateDiscoverer(Assembly assembly)
-    {
+        => new AvaloniaTestFrameworkDiscoverer(new XunitTestAssembly(assembly, null, assembly.GetName().Version));
-    }
 
-    protected override ITestFrameworkExecutor CreateExecutor(AssemblyName assemblyName)
+    protected override ITestFrameworkExecutor CreateExecutor(Assembly assembly)
-        => new Executor(assemblyName, SourceInformationProvider, DiagnosticMessageSink);
+        => new AvaloniaTestFrameworkExecutor(new XunitTestAssembly(assembly, null, assembly.GetName().Version));
-
-
-    private class Executor : XunitTestFrameworkExecutor
-    {
-        public Executor(AssemblyName assemblyName, ISourceInformationProvider sourceInformationProvider,
-            IMessageSink diagnosticMessageSink) : base(assemblyName, sourceInformationProvider,
-            diagnosticMessageSink)
-        {
-        }
-
-        protected override async void RunTestCases(IEnumerable<IXunitTestCase> testCases,
-            IMessageSink executionMessageSink,
-            ITestFrameworkExecutionOptions executionOptions)
-        {
-            using (var assemblyRunner = new AvaloniaTestAssemblyRunner(
-                       TestAssembly, testCases, DiagnosticMessageSink, executionMessageSink,
-                       executionOptions)) await assemblyRunner.RunAsync();
-        }
-    }
 }

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestFrameworkAttribute.cs

@@ -1,8 +1,5 @@
 using System;
-using System.Diagnostics.CodeAnalysis;
+using Xunit.v3;
-using System.Linq;
-using Xunit.Abstractions;
-using Xunit.Sdk;
 
 namespace Avalonia.Headless.XUnit;
 
@@ -12,27 +9,9 @@ namespace Avalonia.Headless.XUnit;
 /// <remarks>
 /// It is an alternative to using [AvaloniaFact] or [AvaloniaTheory] attributes on every test method.
 /// </remarks>
-[TestFrameworkDiscoverer("Avalonia.Headless.XUnit.AvaloniaTestFrameworkTypeDiscoverer", "Avalonia.Headless.XUnit")]
 [AttributeUsage(AttributeTargets.Assembly, AllowMultiple = false)]
 public sealed class AvaloniaTestFrameworkAttribute : Attribute, ITestFrameworkAttribute
 {
-}
+    public Type FrameworkType
-
+        => typeof(AvaloniaTestFramework);
-/// <summary>
-/// Discoverer implementation for the Avalonia testing framework.
-/// </summary>
-public class AvaloniaTestFrameworkTypeDiscoverer : ITestFrameworkTypeDiscoverer
-{
-    /// <summary>
-    /// Creates instance of <see cref="AvaloniaTestFrameworkTypeDiscoverer"/>. 
-    /// </summary>
-    public AvaloniaTestFrameworkTypeDiscoverer(IMessageSink _)
-    {
-    }
-
-    /// <inheritdoc/>
-    public Type GetTestFrameworkType(IAttributeInfo attribute)
-    {
-        return typeof(AvaloniaTestFramework);
-    }
 }

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestFrameworkDiscoverer.cs

@@ -0,0 +1,16 @@
+using Xunit;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaTestFrameworkDiscoverer : XunitTestFrameworkDiscoverer
+{
+    public AvaloniaTestFrameworkDiscoverer(
+        IXunitTestAssembly testAssembly,
+        IXunitTestCollectionFactory? collectionFactory = null)
+        : base(testAssembly, collectionFactory)
+    {
+        DiscovererTypeCache[typeof(FactAttribute)] = typeof(AvaloniaFactDiscoverer);
+        DiscovererTypeCache[typeof(TheoryAttribute)] = typeof(AvaloniaTheoryDiscoverer);
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestFrameworkExecutor.cs

@@ -0,0 +1,19 @@
+using System.Threading.Tasks;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaTestFrameworkExecutor(IXunitTestAssembly testAssembly)
+    : XunitTestFrameworkExecutor(testAssembly)
+{
+    private readonly HeadlessUnitTestSession _session = HeadlessUnitTestSession.GetOrStartForAssembly(testAssembly.Assembly);
+
+    protected override ITestFrameworkDiscoverer CreateDiscoverer()
+        => new AvaloniaTestFrameworkDiscoverer(TestAssembly);
+
+    public override async ValueTask DisposeAsync()
+    {
+        await _session.DisposeAsync();
+        await base.DisposeAsync();
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestRunner.cs

@@ -0,0 +1,50 @@
+using System.Collections.Generic;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Threading;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaTestRunner : XunitTestRunnerBase<AvaloniaTestRunnerContext, IXunitTest>
+{
+    public static AvaloniaTestRunner Instance { get; } = new();
+
+    private AvaloniaTestRunner()
+    {
+    }
+
+    public async ValueTask<RunSummary> Run(
+        IXunitTest test,
+        IMessageBus messageBus,
+        object?[] constructorArguments,
+        ExplicitOption explicitOption,
+        ExceptionAggregator aggregator,
+        CancellationTokenSource cancellationTokenSource,
+        IReadOnlyCollection<IBeforeAfterTestAttribute> beforeAfterAttributes,
+        HeadlessUnitTestSession session)
+    {
+        await using var ctxt = new AvaloniaTestRunnerContext(
+            test,
+            messageBus,
+            explicitOption,
+            aggregator,
+            cancellationTokenSource,
+            beforeAfterAttributes,
+            constructorArguments,
+            session
+        );
+        await ctxt.InitializeAsync();
+
+        return await session.Dispatch(
+            async () =>
+            {
+                var dispatcher = Dispatcher.UIThread;
+                var summary = await Run(ctxt);
+                dispatcher.RunJobs();
+                return summary;
+            },
+            ctxt.CancellationTokenSource.Token);
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTestRunnerContext.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using System.Threading;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+internal sealed class AvaloniaTestRunnerContext(
+    IXunitTest test,
+    IMessageBus messageBus,
+    ExplicitOption explicitOption,
+    ExceptionAggregator aggregator,
+    CancellationTokenSource cancellationTokenSource,
+    IReadOnlyCollection<IBeforeAfterTestAttribute> beforeAfterTestAttributes,
+    object?[] constructorArguments,
+    HeadlessUnitTestSession session)
+    : XunitTestRunnerContext(
+        test,
+        messageBus,
+        explicitOption,
+        aggregator,
+        cancellationTokenSource,
+        beforeAfterTestAttributes,
+        constructorArguments)
+{
+    public HeadlessUnitTestSession Session { get; } = session;
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTheoryAttribute.cs

@@ -1,9 +1,6 @@
 using System;
-using System.Collections.Generic;
-using System.ComponentModel;
 using Xunit;
-using Xunit.Abstractions;
+using Xunit.v3;
-using Xunit.Sdk;
 
 namespace Avalonia.Headless.XUnit;
 
@@ -12,26 +9,5 @@ namespace Avalonia.Headless.XUnit;
 /// such that awaited expressions resume on the test's "main thread".
 /// </summary>
 [AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
-[XunitTestCaseDiscoverer("Avalonia.Headless.XUnit.AvaloniaTheoryDiscoverer", "Avalonia.Headless.XUnit")]
+[XunitTestCaseDiscoverer(typeof(AvaloniaTheoryDiscoverer))]
-public sealed class AvaloniaTheoryAttribute : TheoryAttribute
+public sealed class AvaloniaTheoryAttribute : TheoryAttribute;
-{
-}
-
-[EditorBrowsable(EditorBrowsableState.Never)]
-public class AvaloniaTheoryDiscoverer : TheoryDiscoverer
-{
-    public AvaloniaTheoryDiscoverer(IMessageSink diagnosticMessageSink)
-        : base(diagnosticMessageSink)
-    {
-    }
-
-    protected override IEnumerable<IXunitTestCase> CreateTestCasesForDataRow(ITestFrameworkDiscoveryOptions discoveryOptions, ITestMethod testMethod, IAttributeInfo theoryAttribute, object[] dataRow)
-    {
-        yield return new AvaloniaTestCase(DiagnosticMessageSink, discoveryOptions.MethodDisplayOrDefault(), testMethod, dataRow);
-    }
-
-    protected override IEnumerable<IXunitTestCase> CreateTestCasesForTheory(ITestFrameworkDiscoveryOptions discoveryOptions, ITestMethod testMethod, IAttributeInfo theoryAttribute)
-    {
-        yield return new AvaloniaTheoryTestCase(DiagnosticMessageSink, discoveryOptions.MethodDisplayOrDefault(), TestMethodDisplayOptions.None, testMethod);
-    }
-}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTheoryDiscoverer.cs

@@ -0,0 +1,92 @@
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Internal;
+using Xunit.Sdk;
+using Xunit.v3;
+
+namespace Avalonia.Headless.XUnit;
+
+[EditorBrowsable(EditorBrowsableState.Never)]
+public class AvaloniaTheoryDiscoverer : TheoryDiscoverer
+{
+    protected override ValueTask<IReadOnlyCollection<IXunitTestCase>> CreateTestCasesForDataRow(
+        ITestFrameworkDiscoveryOptions discoveryOptions,
+        IXunitTestMethod testMethod,
+        ITheoryAttribute theoryAttribute,
+        ITheoryDataRow dataRow,
+        object?[] testMethodArguments)
+    {
+        var details = TestIntrospectionHelper.GetTestCaseDetailsForTheoryDataRow(
+            discoveryOptions,
+            testMethod,
+            theoryAttribute,
+            dataRow,
+            testMethodArguments);
+        var traits = TestIntrospectionHelper.GetTraits(testMethod, dataRow);
+
+        var testCase = new AvaloniaTestCase(
+            details.ResolvedTestMethod,
+            details.TestCaseDisplayName,
+            details.UniqueID,
+            details.Explicit,
+            details.SkipExceptions,
+            details.SkipReason,
+            details.SkipType,
+            details.SkipUnless,
+            details.SkipWhen,
+            traits,
+            testMethodArguments,
+            sourceFilePath: details.SourceFilePath,
+            sourceLineNumber: details.SourceLineNumber,
+            timeout: details.Timeout);
+
+        return ValueTask.FromResult<IReadOnlyCollection<IXunitTestCase>>([testCase]);
+    }
+
+    protected override ValueTask<IReadOnlyCollection<IXunitTestCase>> CreateTestCasesForTheory(
+        ITestFrameworkDiscoveryOptions discoveryOptions,
+        IXunitTestMethod testMethod,
+        ITheoryAttribute theoryAttribute)
+    {
+        var details = TestIntrospectionHelper.GetTestCaseDetails(discoveryOptions, testMethod, theoryAttribute);
+
+        var testCase =
+            details.SkipReason is not null && details.SkipUnless is null && details.SkipWhen is null
+                ? new AvaloniaTestCase(
+                    details.ResolvedTestMethod,
+                    details.TestCaseDisplayName,
+                    details.UniqueID,
+                    details.Explicit,
+                    details.SkipExceptions,
+                    details.SkipReason,
+                    details.SkipType,
+                    details.SkipUnless,
+                    details.SkipWhen,
+                    testMethod.Traits.ToReadWrite(StringComparer.OrdinalIgnoreCase),
+                    sourceFilePath: details.SourceFilePath,
+                    sourceLineNumber: details.SourceLineNumber,
+                    timeout: details.Timeout
+                )
+                : (IXunitTestCase)new AvaloniaDelayEnumeratedTheoryTestCase(
+                    details.ResolvedTestMethod,
+                    details.TestCaseDisplayName,
+                    details.UniqueID,
+                    details.Explicit,
+                    theoryAttribute.SkipTestWithoutData,
+                    details.SkipExceptions,
+                    details.SkipReason,
+                    details.SkipType,
+                    details.SkipUnless,
+                    details.SkipWhen,
+                    testMethod.Traits.ToReadWrite(StringComparer.OrdinalIgnoreCase),
+                    sourceFilePath: details.SourceFilePath,
+                    sourceLineNumber: details.SourceLineNumber,
+                    timeout: details.Timeout
+                );
+
+        return ValueTask.FromResult<IReadOnlyCollection<IXunitTestCase>>([testCase]);
+    }
+}

src/Headless/Avalonia.Headless.XUnit/AvaloniaTheoryTestCase.cs

@@ -1,31 +0,0 @@
-using System;
-using System.ComponentModel;
-using System.Threading;
-using System.Threading.Tasks;
-using Xunit.Abstractions;
-using Xunit.Sdk;
-
-namespace Avalonia.Headless.XUnit;
-
-internal class AvaloniaTheoryTestCase : XunitTheoryTestCase
-{
-    [EditorBrowsable(EditorBrowsableState.Never)]
-    [Obsolete("Called by the de-serializer; should only be called by deriving classes for de-serialization purposes")]
-    public AvaloniaTheoryTestCase()
-    {
-    }
-
-    public AvaloniaTheoryTestCase(IMessageSink diagnosticMessageSink, TestMethodDisplay defaultMethodDisplay, TestMethodDisplayOptions defaultMethodDisplayOptions, ITestMethod testMethod)
-        : base(diagnosticMessageSink, defaultMethodDisplay, defaultMethodDisplayOptions, testMethod)
-    {
-    }
-    
-    public override Task<RunSummary> RunAsync(IMessageSink diagnosticMessageSink, IMessageBus messageBus, object[] constructorArguments, ExceptionAggregator aggregator, CancellationTokenSource cancellationTokenSource)
-    {
-        var session = HeadlessUnitTestSession.GetOrStartForAssembly(Method.ToRuntimeMethod().DeclaringType?.Assembly);
-
-        return AvaloniaTestCaseRunner
-            .RunTest(session, this, DisplayName, SkipReason, constructorArguments,
-                TestMethodArguments, messageBus, aggregator, cancellationTokenSource);
-    }
-}

src/Headless/Avalonia.Headless/HeadlessUnitTestSession.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Headless;
 /// All UI tests are supposed to be executed from one of the <see cref="Dispatch"/> methods to keep execution flow on the UI thread.
 /// Disposing unit test session stops internal dispatcher loop. 
 /// </summary>
-public sealed class HeadlessUnitTestSession : IDisposable
+public sealed class HeadlessUnitTestSession : IDisposable, IAsyncDisposable
 {
     private static readonly Dictionary<Assembly, HeadlessUnitTestSession> s_session = new();
 
@@ -184,6 +184,14 @@ public sealed class HeadlessUnitTestSession : IDisposable
         _cancellationTokenSource.Dispose();
     }
 
+    public async ValueTask DisposeAsync()
+    {
+        await _cancellationTokenSource.CancelAsync().ConfigureAwait(false);
+        _queue.CompleteAdding();
+        await _dispatchTask.ConfigureAwait(false);
+        _cancellationTokenSource.Dispose();
+    }
+
     /// <summary>
     /// Creates instance of <see cref="HeadlessUnitTestSession"/>. 
     /// </summary>

tests/Avalonia.Headless.XUnit.PerAssembly.UnitTests/Avalonia.Headless.XUnit.PerAssembly.UnitTests.csproj

@@ -4,7 +4,6 @@
     <OutputType>Exe</OutputType>
     <IsTestProject>true</IsTestProject>
     <DefineConstants>$(DefineConstants);XUNIT</DefineConstants>
-    <IsXUnit2>true</IsXUnit2>
   </PropertyGroup>
 
   <Import Project="..\..\build\UnitTests.NetCore.targets" />

tests/Avalonia.Headless.XUnit.PerTest.UnitTests/Avalonia.Headless.XUnit.PerTest.UnitTests.csproj

@@ -4,7 +4,6 @@
     <OutputType>Exe</OutputType>
     <IsTestProject>true</IsTestProject>
     <DefineConstants>$(DefineConstants);XUNIT</DefineConstants>
-    <IsXUnit2>true</IsXUnit2>
   </PropertyGroup>
 
   <Import Project="..\..\build\UnitTests.NetCore.targets" />

tests/Avalonia.IntegrationTests.Win32/Avalonia.IntegrationTests.Win32.csproj

@@ -13,10 +13,7 @@
     <ProjectReference Include="../../src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
+  <Import Project="../../build/XUnit.props" />
-    <PackageReference Include="xunit.v3.mtp-v2" Version="3.2.1" />
-  </ItemGroup>
-  
   <Import Project="../../build/SharedVersion.props" />
   <Import Project="../../build/ReferenceCoreLibraries.props" />
   <Import Project="../../build/BuildTargets.targets" />