fix: resolve code fixer merge conflict markers in multi-target projects

TUnit.Analyzers.CodeFixers/TwoPhase/MSTestTwoPhaseAnalyzer.cs

@@ -122,7 +122,13 @@ private bool VerifyMSTestNamespace(InvocationExpressionSyntax invocation)
             if (symbolInfo.Symbol is IMethodSymbol methodSymbol)
             {
                 var containingNamespace = methodSymbol.ContainingType?.ContainingNamespace?.ToDisplayString();
-                return containingNamespace?.StartsWith("Microsoft.VisualStudio.TestTools.UnitTesting") == true;
+                // Only return false if we positively know it's NOT MSTest
+                if (containingNamespace != null && !containingNamespace.StartsWith("Microsoft.VisualStudio.TestTools.UnitTesting"))
+                {
+                    return false;
+                }
+                // Namespace matches or is null (resolution failed) - assume it's MSTest
+                return true;
             }
         }
         catch

TUnit.Analyzers.CodeFixers/TwoPhase/NUnitTwoPhaseAnalyzer.cs

@@ -109,7 +109,13 @@ private bool VerifyNUnitNamespace(InvocationExpressionSyntax invocation)
             if (symbolInfo.Symbol is IMethodSymbol methodSymbol)
             {
                 var containingNamespace = methodSymbol.ContainingType?.ContainingNamespace?.ToDisplayString();
-                return containingNamespace?.StartsWith("NUnit.Framework") == true;
+                // Only return false if we positively know it's NOT NUnit
+                if (containingNamespace != null && !containingNamespace.StartsWith("NUnit.Framework"))
+                {
+                    return false;
+                }
+                // Namespace matches or is null (resolution failed) - assume it's NUnit
+                return true;
             }
         }
         catch

TUnit.Analyzers.CodeFixers/TwoPhase/XUnitTwoPhaseAnalyzer.cs

@@ -103,12 +103,28 @@ private bool IsXUnitAssertion(InvocationExpressionSyntax invocation)
                 if (XUnitAssertMethods.Contains(methodName))
                 {
                     // Semantic check to confirm it's xUnit
-                    var symbolInfo = SemanticModel.GetSymbolInfo(invocation);
-                    if (symbolInfo.Symbol is IMethodSymbol methodSymbol)
+                    try
                     {
-                        var containingType = methodSymbol.ContainingType?.ToDisplayString();
-                        return containingType?.StartsWith("Xunit.Assert") == true;
+                        var symbolInfo = SemanticModel.GetSymbolInfo(invocation);
+                        if (symbolInfo.Symbol is IMethodSymbol methodSymbol)
+                        {
+                            var containingType = methodSymbol.ContainingType?.ToDisplayString();
+                            // Only return false if we positively know it's NOT xUnit
+                            if (containingType != null && !containingType.StartsWith("Xunit.Assert"))
+                            {
+                                return false;
+                            }
+                            // Namespace matches or is null (resolution failed) - assume it's xUnit
+                            return true;
+                        }
                     }
+                    catch
+                    {
+                        // Fall back to syntax-based detection
+                    }
+
+                    // Semantic check failed or symbol not found - assume it's xUnit if syntax matches
+                    return true;
                 }
             }
         }