Expose test arguments as filterable properties

  Parameterized tests can now be filtered by their resolved argument
  values via `--treenode-filter`, e.g.:

      --treenode-filter "/*/*/MyTests/*[arg0=*foo*]"

  TestBuilder.InvokeDiscoveryEventReceiversAsync stringifies each entry
  in TestDetails.TestMethodArguments and adds it to the DiscoveredTestContext
  as arg0, arg1, ... so it flows into the existing property bag used by
  the filter matcher. Wildcards in the value are supported by the platform's
  built-in matcher.

Author: SimonCropp

TUnit.Engine.Tests/FilterByArgumentValueFilteringTests.cs

@@ -0,0 +1,21 @@
+using Shouldly;
+using TUnit.Engine.Tests.Enums;
+
+namespace TUnit.Engine.Tests;
+
+public class FilterByArgumentValueFilteringTests(TestMode testMode) : InvokableTestBase(testMode)
+{
+    [Test]
+    public async Task ExactMatch()
+    {
+        await RunTestsWithFilter(
+            "/*/*/FilterByArgumentValueTests/*[arg0=beta]",
+            [
+                result => result.ResultSummary.Outcome.ShouldBe("Completed"),
+                result => result.ResultSummary.Counters.Total.ShouldBe(1),
+                result => result.ResultSummary.Counters.Passed.ShouldBe(1),
+                result => result.ResultSummary.Counters.Failed.ShouldBe(0),
+                result => result.ResultSummary.Counters.NotExecuted.ShouldBe(0)
+            ]);
+    }
+}

TUnit.Engine/Building/TestBuilder.cs

@@ -1126,6 +1126,16 @@ private Task InvokeDiscoveryEventReceiversAsync(TestContext context)
             context.Metadata.TestDetails.TestName,
             context);
 
+        // Expose the resolved method argument values as filterable properties so
+        // callers can use `--treenode-filter` with syntax like `MyTest[arg0=*foo*]`
+        // to target a specific parameterized instance.
+        var testMethodArguments = context.Metadata.TestDetails.TestMethodArguments;
+        for (var i = 0; i < testMethodArguments.Length; i++)
+        {
+            var argValue = testMethodArguments[i]?.ToString() ?? "";
+            discoveredContext.AddProperty($"arg{i}", argValue);
+        }
+
         return _eventReceiverOrchestrator.InvokeTestDiscoveryEventReceiversAsync(context, discoveredContext, CancellationToken.None);
     }
 

TUnit.TestProject/FilterByArgumentValueTests.cs

@@ -0,0 +1,12 @@
+namespace TUnit.TestProject;
+
+public class FilterByArgumentValueTests
+{
+    [Test]
+    [Arguments("alpha")]
+    [Arguments("beta")]
+    [Arguments("gamma")]
+    public void Test(string value)
+    {
+    }
+}