From 1e1e46b9d01985dd291e485b279ecb4239a08125 Mon Sep 17 00:00:00 2001
From: Tom Longhurst <30480171+thomhurst@users.noreply.github.com>
Date: Thu, 28 May 2026 19:36:05 +0100
Subject: [PATCH] perf: dedupe TestDataFormatter.FormatArguments with pooled
 StringBuilder

Collapse the two duplicated FormatArguments overloads into one canonical
implementation. The no-formatter overload now delegates to the formatter
overload. Replace the string[] + string.Join intermediate allocation with
a pooled StringBuilder from TUnit.Core.Helpers.StringBuilderPool.

Behavior is identical; this reduces per-row allocations during display-name
and data formatting.

Closes #6038
---
 TUnit.Core/DataSources/TestDataFormatter.cs | 33 ++++++++++-----------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/TUnit.Core/DataSources/TestDataFormatter.cs b/TUnit.Core/DataSources/TestDataFormatter.cs
index c7ecdf87cb..b1cd16f0aa 100644
--- a/TUnit.Core/DataSources/TestDataFormatter.cs
+++ b/TUnit.Core/DataSources/TestDataFormatter.cs
@@ -26,31 +26,30 @@ public static string FormatArguments(object?[] arguments, List<Func<object?, str
             return string.Empty;
         }
 
-        var formattedArgs = new string[arguments.Length];
-        for (var i = 0; i < arguments.Length; i++)
+        var builder = StringBuilderPool.Get();
+        try
         {
-            formattedArgs[i] = ArgumentFormatter.Format(arguments[i], formatters);
+            for (var i = 0; i < arguments.Length; i++)
+            {
+                if (i > 0)
+                {
+                    builder.Append(", ");
+                }
+                builder.Append(ArgumentFormatter.Format(arguments[i], formatters));
+            }
+            return builder.ToString();
+        }
+        finally
+        {
+            StringBuilderPool.Return(builder);
         }
-        return string.Join(", ", formattedArgs);
     }
 
     /// <summary>
     /// Formats an array of arguments using default formatting
     /// </summary>
     public static string FormatArguments(object?[] arguments)
-    {
-        if (arguments.Length == 0)
-        {
-            return string.Empty;
-        }
-
-        var formattedArgs = new string[arguments.Length];
-        for (var i = 0; i < arguments.Length; i++)
-        {
-            formattedArgs[i] = ArgumentFormatter.Format(arguments[i], []);
-        }
-        return string.Join(", ", formattedArgs);
-    }
+        => FormatArguments(arguments, []);
 
     /// <summary>
     /// Creates a display name from test metadata and arguments