feat: use results directory provided by Microsoft Testing Platform in HtmlReporter

TUnit.Engine/Extensions/TestApplicationBuilderExtensions.cs

@@ -7,6 +7,7 @@
 using TUnit.Engine.Framework;
 using TUnit.Engine.Reporters;
 using Microsoft.Testing.Platform.CommandLine;
+using Microsoft.Testing.Platform.Configurations;
 
 #pragma warning disable TPEXP
 
@@ -79,6 +80,11 @@ public static void AddTUnit(this ITestApplicationBuilder testApplicationBuilder)
             {
                 junitReporter.SetOutputPath(pathArgs[0]);
             }
+
+            // Set results directory as specified by --results-directory,
+            // so it can be used in the default output path if --report-html-filename is not provided
+            junitReporter.SetResultsDirectory(serviceProvider.GetRequiredService<IConfiguration>().GetTestResultDirectory());
+
             return junitReporter;
         });
         testApplicationBuilder.TestHost.AddTestHostApplicationLifetime(_ => junitReporter);
@@ -106,6 +112,10 @@ public static void AddTUnit(this ITestApplicationBuilder testApplicationBuilder)
             // OnTestSessionFinishingAsync (called before the bus is drained/disabled).
             htmlReporter.SetMessageBus(serviceProvider.GetMessageBus());
 
+            // Set results directory as specified by --results-directory,
+            // so it can be used in the default output path if --report-html-filename is not provided
+            htmlReporter.SetResultsDirectory(serviceProvider.GetRequiredService<IConfiguration>().GetTestResultDirectory());
+
             return htmlReporter;
         });
     }

TUnit.Engine/Reporters/Html/HtmlReporter.cs

@@ -23,6 +23,7 @@ internal sealed class HtmlReporter(IExtension extension) : IDataConsumer, IDataP
 {
     private string? _outputPath;
     private IMessageBus? _messageBus;
+    private string _resultsDirectory = "TestResults";
     private readonly ConcurrentDictionary<string, ConcurrentQueue<TestNodeUpdateMessage>> _updates = [];
 
 #if NET
@@ -64,11 +65,6 @@ public Task ConsumeAsync(IDataProducer dataProducer, IData value, CancellationTo
 
     public Task BeforeRunAsync(CancellationToken cancellationToken)
     {
-        if (string.IsNullOrEmpty(_outputPath))
-        {
-            _outputPath = GetDefaultOutputPath();
-        }
-
 #if NET
         _activityCollector = new ActivityCollector();
         _activityCollector.Start();
@@ -117,6 +113,11 @@ public async Task OnTestSessionFinishingAsync(ITestSessionContext testSessionCon
                 return;
             }
 
+            if (string.IsNullOrEmpty(_outputPath))
+            {
+                _outputPath = GetDefaultOutputPath();
+            }
+
             var outputPath = _outputPath!;
             // WriteFileAsync returns false if all retry attempts are exhausted (locked file, bad path, etc.).
             // Artifact publishing is gated on a successful write — no file means no artifact.
@@ -178,6 +179,13 @@ internal void SetMessageBus(IMessageBus? messageBus)
         _messageBus = messageBus;
     }
 
+    // Called by the AddTestSessionLifetimeHandler factory at startup, before any session events fire,
+    // so _resultsDirectory is guaranteed to be set before OnTestSessionFinishingAsync is invoked.
+    internal void SetResultsDirectory(string path)
+    {
+        _resultsDirectory = path;
+    }
+
     private ReportData BuildReportData()
     {
         var assemblyName = Assembly.GetEntryAssembly()?.GetName().Name ?? "TestResults";
@@ -527,13 +535,13 @@ private static (string Status, ReportExceptionData? Exception, string? SkipReaso
         };
     }
 
-    private static string GetDefaultOutputPath()
+    private string GetDefaultOutputPath()
     {
         var assemblyName = Assembly.GetEntryAssembly()?.GetName().Name ?? "TestResults";
         var sanitizedName = string.Concat(assemblyName.Split(Path.GetInvalidFileNameChars()));
         var os = GetShortOsName();
         var tfm = GetShortFrameworkName();
-        return Path.GetFullPath(Path.Combine("TestResults", $"{sanitizedName}-{os}-{tfm}-report.html"));
+        return Path.GetFullPath(Path.Combine(_resultsDirectory, $"{sanitizedName}-{os}-{tfm}-report.html"));
     }
 
     private static string GetShortOsName()

TUnit.Engine/Reporters/JUnitReporter.cs

@@ -16,6 +16,7 @@ public class JUnitReporter(IExtension extension) : IDataConsumer, ITestHostAppli
 {
     private string _outputPath = null!;
     private bool _isEnabled;
+    private string _resultsDirectory = "TestResults";
 
     public async Task<bool> IsEnabledAsync()
     {
@@ -35,16 +36,6 @@ public async Task<bool> IsEnabledAsync()
             return false;
         }
 
-        // Determine output path (only if not already set via command-line argument)
-        if (string.IsNullOrEmpty(_outputPath))
-        {
-            var envPath = Environment.GetEnvironmentVariable(EnvironmentConstants.JUnitXmlOutputPath);
-
-            _outputPath = envPath is not null
-                ? PathValidator.ValidateAndNormalizePath(envPath, nameof(EnvironmentConstants.JUnitXmlOutputPath))
-                : GetDefaultOutputPath();
-        }
-
         _isEnabled = true;
         return await extension.IsEnabledAsync();
     }
@@ -97,6 +88,16 @@ public async Task AfterRunAsync(int exitCode, CancellationToken cancellation)
             return;
         }
 
+        // Determine output path (only if not already set via command-line argument)
+        if (string.IsNullOrEmpty(_outputPath))
+        {
+            var envPath = Environment.GetEnvironmentVariable(EnvironmentConstants.JUnitXmlOutputPath);
+
+            _outputPath = envPath is not null
+                ? PathValidator.ValidateAndNormalizePath(envPath, nameof(EnvironmentConstants.JUnitXmlOutputPath))
+                : GetDefaultOutputPath();
+        }
+
         // Write to file with retry logic
         await WriteXmlFileAsync(_outputPath, xmlContent, cancellation);
     }
@@ -108,14 +109,21 @@ internal void SetOutputPath(string path)
         _outputPath = PathValidator.ValidateAndNormalizePath(path, nameof(path));
     }
 
-    private static string GetDefaultOutputPath()
+    // Called by the AddTestSessionLifetimeHandler factory at startup, before any session events fire,
+    // so _resultsDirectory is guaranteed to be set before AfterRunAsync is invoked.
+    internal void SetResultsDirectory(string path)
+    {
+        _resultsDirectory = path;
+    }
+
+    private string GetDefaultOutputPath()
     {
         var assemblyName = Assembly.GetEntryAssembly()?.GetName().Name ?? "TestResults";
 
         // Sanitize assembly name to remove any characters that could be used for path traversal
         var sanitizedName = string.Concat(assemblyName.Split(Path.GetInvalidFileNameChars()));
 
-        return Path.GetFullPath(Path.Combine("TestResults", $"{sanitizedName}-junit.xml"));
+        return Path.GetFullPath(Path.Combine(_resultsDirectory, $"{sanitizedName}-junit.xml"));
     }
 
     private static async Task WriteXmlFileAsync(string path, string content, CancellationToken cancellationToken)