perf: eliminate eager testFullName allocation in MSTestTestNodeConverter

src/Adapter/MSTest.TestAdapter/TestingPlatformAdapter/MSTestTestNodeConverter.cs

@@ -85,12 +85,14 @@ public static TestNode ToResultTestNode(UnitTestElement element, FrameworkTestRe
     private static TestNode CreateBaseTestNode(UnitTestElement element, bool isTrxEnabled, string? displayNameOverride)
     {
         TestMethod testMethod = element.TestMethod;
-        string testFullName = $"{testMethod.FullClassName}.{testMethod.Name}";
 
         TestNode testNode = new()
         {
             Uid = new TestNodeUid(element.GetTestId().ToString()),
-            DisplayName = displayNameOverride ?? testMethod.DisplayName ?? testFullName,
+
+            // TestMethod.DisplayName is always initialized (the constructor sets it to displayName ?? name), so
+            // displayNameOverride is the only real fallback needed here.
+            DisplayName = displayNameOverride ?? testMethod.DisplayName,
         };
 
         AddCategoriesAndTraits(testNode, element, isTrxEnabled);
@@ -194,8 +196,9 @@ private static void AddTrxResultProperties(TestNode testNode, UnitTestElement el
         }
 
         TestMethod testMethod = element.TestMethod;
-        string testFullName = $"{testMethod.FullClassName}.{testMethod.Name}";
-        testNode.Properties.Add(new TrxTestDefinitionName(testMethod.DisplayName ?? testFullName));
+
+        // TestMethod.DisplayName is always initialized (constructor sets it to displayName ?? name).
+        testNode.Properties.Add(new TrxTestDefinitionName(testMethod.DisplayName));
 
         TestMethodIdentifierProperty? testMethodIdentifierProperty = testNode.Properties.SingleOrDefault<TestMethodIdentifierProperty>();
         if (testMethodIdentifierProperty is not null)
@@ -205,13 +208,15 @@ private static void AddTrxResultProperties(TestNode testNode, UnitTestElement el
                     ? testMethodIdentifierProperty.TypeName
                     : $"{testMethodIdentifierProperty.Namespace}.{testMethodIdentifierProperty.TypeName}"));
         }
-        else if (TryParseFullyQualifiedType(testFullName, out string? fullyQualifiedType))
+        else if (!StringEx.IsNullOrEmpty(testMethod.FullClassName))
         {
-            testNode.Properties.Add(new TrxFullyQualifiedTypeNameProperty(fullyQualifiedType));
+            // FullClassName is the source of truth for the type name, so use it directly instead of re-parsing it out
+            // of a "FullClassName.Name" string.
+            testNode.Properties.Add(new TrxFullyQualifiedTypeNameProperty(testMethod.FullClassName));
         }
         else
         {
-            throw new InvalidOperationException("Unable to parse fully qualified type name from test: " + testFullName);
+            throw new InvalidOperationException($"The test method '{testMethod.Name}' does not have a fully qualified class name.");
         }
     }
 
@@ -291,22 +296,5 @@ private static void AddAttachments(TestNode testNode, FrameworkTestResult result
             testNode.Properties.Add(new FileArtifactProperty(new FileInfo(pathToResultFile), Resource.AttachmentSetDisplayName, resultFile));
         }
     }
-
-    private static bool TryParseFullyQualifiedType(string fullyQualifiedName, [NotNullWhen(true)] out string? fullyQualifiedType)
-    {
-        fullyQualifiedType = null;
-
-        int openBracketIndex = fullyQualifiedName.IndexOf('(');
-        int lastDotIndexBeforeOpenBracket = openBracketIndex <= 0
-            ? fullyQualifiedName.LastIndexOf('.')
-            : fullyQualifiedName.LastIndexOf('.', openBracketIndex - 1);
-        if (lastDotIndexBeforeOpenBracket <= 0)
-        {
-            return false;
-        }
-
-        fullyQualifiedType = fullyQualifiedName[..lastDotIndexBeforeOpenBracket];
-        return true;
-    }
 }
 #endif

test/UnitTests/MSTestAdapter.UnitTests/MSTestTestNodeConverterTests.cs

@@ -230,6 +230,22 @@ public void ToResultTestNode_AddsTrxProperties_WhenTrxEnabled()
         typeName!.FullyQualifiedTypeName.Should().Be("MyNamespace.MyClass");
     }
 
+    public void ToResultTestNode_UsesFullClassNameForTrxTypeName_WhenNoManagedMethodName()
+    {
+        // Without a managed method name, no TestMethodIdentifierProperty is added, so the TRX fully-qualified type
+        // name falls back to TestMethod.FullClassName directly (the behavior that replaced TryParseFullyQualifiedType).
+        UnitTestElement element = CreateElement(managedMethodName: null);
+        var result = new FrameworkTestResult { Outcome = UnitTestOutcome.Failed, ExceptionMessage = "boom", ExceptionStackTrace = "at X()" };
+
+        TestNode node = MSTestTestNodeConverter.ToResultTestNode(element, result, DateTimeOffset.Now, DateTimeOffset.Now, isTrxEnabled: true, new MSTestSettings());
+
+        node.Properties.Any<TestMethodIdentifierProperty>().Should().BeFalse();
+        Testing.Extensions.TrxReport.Abstractions.TrxFullyQualifiedTypeNameProperty? typeName =
+            node.Properties.SingleOrDefault<Testing.Extensions.TrxReport.Abstractions.TrxFullyQualifiedTypeNameProperty>();
+        typeName.Should().NotBeNull();
+        typeName!.FullyQualifiedTypeName.Should().Be("MyNamespace.MyClass");
+    }
+
     public void ToResultTestNode_DoesNotAddTrxProperties_WhenTrxDisabled()
     {
         TestNode node = ResultNode(UnitTestOutcome.Passed);