From d7c3fbc41de73c32626dc1bdf81f8fc45509d8e7 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Fri, 4 Sep 2026 20:00:52 +0000
Subject: [PATCH] test: Add unit tests for CatmullRomPath.SetLooping and fix
 localT calculation

Co-authored-by: johnstrand <11484777+johnstrand@users.noreply.github.com>
---
 src/GameUtils/Math/CatmullRom.cs              |  5 ++-
 .../Math/CatmullRomPathTests.cs               | 38 +++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/src/GameUtils/Math/CatmullRom.cs b/src/GameUtils/Math/CatmullRom.cs
index 2488101..ed59730 100644
--- a/src/GameUtils/Math/CatmullRom.cs
+++ b/src/GameUtils/Math/CatmullRom.cs
@@ -111,15 +111,16 @@ private void GetSegmentAndLocalT(float t, out int segmentIndex, out float localT
         var segmentCount = _loop ? _points.Count : _points.Count - 1;
         var scaled = t * segmentCount;
         segmentIndex = (int)MathF.Floor(scaled);
-        localT = scaled - segmentIndex;
 
         if (_loop)
         {
-            segmentIndex = segmentIndex % segmentCount;
+            segmentIndex = ((segmentIndex % segmentCount) + segmentCount) % segmentCount;
+            localT = scaled - MathF.Floor(scaled);
         }
         else
         {
             segmentIndex = System.Math.Clamp(segmentIndex, 0, segmentCount - 1);
+            localT = scaled - segmentIndex;
         }
     }
 
diff --git a/tests/GameUtils.Tests/Math/CatmullRomPathTests.cs b/tests/GameUtils.Tests/Math/CatmullRomPathTests.cs
index 7ecfbfe..ac13c58 100644
--- a/tests/GameUtils.Tests/Math/CatmullRomPathTests.cs
+++ b/tests/GameUtils.Tests/Math/CatmullRomPathTests.cs
@@ -134,4 +134,42 @@ public void GetTangent_Looping_EvaluatesTangentCorrectly()
         var tangentStart = path.GetTangent(0f);
         Assert.AreNotEqual(Vector2.Zero, tangentStart);
     }
+
+    [TestMethod]
+    public void SetLooping_True_AlignsPositionAndTangentAtEndpoints()
+    {
+        var path = new CatmullRomPath()
+            .SetLooping(true)
+            .AddPoint(new Vector2(0, 0))
+            .AddPoint(new Vector2(10, 0))
+            .AddPoint(new Vector2(10, 10))
+            .AddPoint(new Vector2(0, 10));
+
+        var pStart = path.GetPoint(0f);
+        var pEnd = path.GetPoint(1f);
+        Assert.AreEqual(pStart, pEnd);
+
+        var tangentStart = path.GetTangent(0f);
+        var tangentEnd = path.GetTangent(1f);
+        Assert.AreEqual(tangentStart.X, tangentEnd.X, 1e-4f);
+        Assert.AreEqual(tangentStart.Y, tangentEnd.Y, 1e-4f);
+    }
+
+    [TestMethod]
+    public void SetLooping_CanToggleLoopingState()
+    {
+        var path = new CatmullRomPath()
+            .AddPoint(new Vector2(0, 0))
+            .AddPoint(new Vector2(10, 0))
+            .AddPoint(new Vector2(10, 10))
+            .AddPoint(new Vector2(0, 10));
+
+        path.SetLooping(true);
+        var pEndLoop = path.GetPoint(1f);
+        Assert.AreEqual(new Vector2(0, 0), pEndLoop);
+
+        path.SetLooping(false);
+        var pEndNonLoop = path.GetPoint(1f);
+        Assert.AreEqual(new Vector2(0, 10), pEndNonLoop);
+    }
 }