Support SetUp and TearDown methods by NUnit

src/Headless/Avalonia.Headless.NUnit/AvaloniaTestCommand.cs

@@ -1,4 +1,6 @@
-using System.Threading.Tasks;
+using System;
+using System.Reflection;
+using System.Threading.Tasks;
 using NUnit.Framework.Interfaces;
 using NUnit.Framework.Internal;
 using NUnit.Framework.Internal.Commands;
@@ -9,6 +11,11 @@ internal class AvaloniaTestCommand : DelegatingTestCommand
 {
     private readonly HeadlessUnitTestSession _session;
 
+    private static FieldInfo s_beforeTest = typeof(BeforeAndAfterTestCommand)
+        .GetField("BeforeTest", BindingFlags.Instance | BindingFlags.NonPublic)!;
+    private static FieldInfo s_afterTest = typeof(BeforeAndAfterTestCommand)
+        .GetField("AfterTest", BindingFlags.Instance | BindingFlags.NonPublic)!;
+    
     public AvaloniaTestCommand(HeadlessUnitTestSession session, TestCommand innerCommand)
         : base(innerCommand)
     {
@@ -23,25 +30,41 @@ internal class AvaloniaTestCommand : DelegatingTestCommand
     // Unfortunately, NUnit has issues with custom synchronization contexts, which means we need to add some hacks to make it work.
     private async Task<TestResult> ExecuteTestMethod(TestExecutionContext context)
     {
-        var testMethod = innerCommand.Test.Method;
-        var methodInfo = testMethod!.MethodInfo;
-
-        var result = methodInfo.Invoke(context.TestObject, innerCommand.Test.Arguments);
-        // Only Task, non generic ValueTask are supported in async context. No ValueTask<> nor F# tasks.
-        if (result is Task task)
-        {
-            await task;
-        }
-        else if (result is ValueTask valueTask)
+        try
         {
-            await valueTask;
-        }
+            if (innerCommand is BeforeAndAfterTestCommand beforeTestCommand)
+            {
+                (s_beforeTest.GetValue(beforeTestCommand) as Action<TestExecutionContext>)?.Invoke(context);
+            }
+
+            var testMethod = innerCommand.Test.Method;
+            var methodInfo = testMethod!.MethodInfo;
 
-        context.CurrentResult.SetResult(ResultState.Success);
+            var result = methodInfo.Invoke(context.TestObject, innerCommand.Test.Arguments);
+            // Only Task, non generic ValueTask are supported in async context. No ValueTask<> nor F# tasks.
+            if (result is Task task)
+            {
+                await task;
+            }
+            else if (result is ValueTask valueTask)
+            {
+                await valueTask;
+            }
 
-        if (context.CurrentResult.AssertionResults.Count > 0)
-            context.CurrentResult.RecordTestCompletion();
+            context.CurrentResult.SetResult(ResultState.Success);
 
-        return context.CurrentResult;
+            if (context.CurrentResult.AssertionResults.Count > 0)
+                context.CurrentResult.RecordTestCompletion();
+
+            return context.CurrentResult;
+        }
+        finally
+        {
+            if (innerCommand is BeforeAndAfterTestCommand beforeTestCommand
+                && context.ExecutionStatus != TestExecutionStatus.AbortRequested)
+            {
+                (s_afterTest.GetValue(beforeTestCommand) as Action<TestExecutionContext>)?.Invoke(context);
+            }
+        }
     }
 }

tests/Avalonia.Headless.UnitTests/InputTests.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Reactive.Disposables;
 using Avalonia.Controls;
 using Avalonia.Input;
 using Avalonia.Layout;
@@ -6,7 +8,27 @@ using Avalonia.Threading;
 namespace Avalonia.Headless.UnitTests;
 
 public class InputTests
+#if XUNIT
+    : IDisposable
+#endif
 {
+    private Window _window;
+
+#if NUNIT
+    [SetUp]
+    public void SetUp()
+#elif XUNIT
+    public InputTests()
+#endif
+    {
+        Dispatcher.UIThread.VerifyAccess();
+        _window = new Window
+        {
+            Width = 100,
+            Height = 100
+        };
+    }
+    
     [AvaloniaFact]
     public void Should_Click_Button_On_Window()
     {
@@ -18,18 +40,24 @@ public class InputTests
         };
 
         button.Click += (_, _) => buttonClicked = true;
+        
+        _window.Content = button;
+        _window.Show();
 
-        var window = new Window
-        {
-            Width = 100,
-            Height = 100,
-            Content = button
-        };
-        window.Show();
-
-        window.MouseDown(new Point(50, 50), MouseButton.Left);
-        window.MouseUp(new Point(50, 50), MouseButton.Left);
+        _window.MouseDown(new Point(50, 50), MouseButton.Left);
+        _window.MouseUp(new Point(50, 50), MouseButton.Left);
 
         Assert.True(buttonClicked);
     }
+
+#if NUNIT
+    [TearDown]
+    public void TearDown()
+#elif XUNIT
+    public void Dispose()
+#endif
+    {
+        Dispatcher.UIThread.VerifyAccess();
+        _window.Close();
+    }
 }