From 96542c655e621bca281024a16f0c193181ed1c63 Mon Sep 17 00:00:00 2001
From: Tom Longhurst <30480171+thomhurst@users.noreply.github.com>
Date: Tue, 27 Jan 2026 00:59:24 +0000
Subject: [PATCH] fix: pass empty array to params parameter when [Arguments]
 has no values

When [Arguments] is used with no arguments and the test method has a
params parameter, the parameter now correctly receives an empty array
instead of null. This matches standard C# behavior where calling a
method with params and no arguments passes an empty array.

Fixes #4561

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
---
 TUnit.Core/Attributes/TestData/ArgumentsAttribute.cs |  6 +++++-
 TUnit.TestProject/ParamsArgumentsTests.cs            | 11 +++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/TUnit.Core/Attributes/TestData/ArgumentsAttribute.cs b/TUnit.Core/Attributes/TestData/ArgumentsAttribute.cs
index 974ebd8232..8ad3d88d69 100644
--- a/TUnit.Core/Attributes/TestData/ArgumentsAttribute.cs
+++ b/TUnit.Core/Attributes/TestData/ArgumentsAttribute.cs
@@ -62,10 +62,14 @@ public sealed class ArgumentsAttribute : Attribute, IDataSourceAttribute, ITestR
 
     public ArgumentsAttribute(params object?[]? values)
     {
-        if (values == null || values.Length == 0)
+        if (values == null)
         {
             Values = [null];
         }
+        else if (values.Length == 0)
+        {
+            Values = [];
+        }
         else
         {
             Values = values;
diff --git a/TUnit.TestProject/ParamsArgumentsTests.cs b/TUnit.TestProject/ParamsArgumentsTests.cs
index 78ad3eb7fe..d13feaf495 100644
--- a/TUnit.TestProject/ParamsArgumentsTests.cs
+++ b/TUnit.TestProject/ParamsArgumentsTests.cs
@@ -44,6 +44,17 @@ public async Task EmptyParamsArray(string name, params Type[] types)
         await Assert.That(types.Length).IsEqualTo(0);
     }
 
+    [Test]
+    [Arguments]
+    [Arguments("a")]
+    [Arguments("a", "b")]
+    [Arguments("a", "b", "c")]
+    public async Task ParamsOnlyWithEmptyArguments(params string[] args)
+    {
+        // When [Arguments] has no values, params should be an empty array, not null
+        await Assert.That(args).IsNotNull();
+    }
+
     [Test]
     [Arguments(1, "single")]
     public async Task SingleStringInParamsArray(int id, params string[] values)