From a60a963a0060bc5105d77dbcce903d90c835462f Mon Sep 17 00:00:00 2001
From: Victor Giers <mail@victorgiers.com>
Date: Thu, 21 May 2026 07:58:40 +0200
Subject: [PATCH] Add boundary checks for top edge key collection

---
 tests/geometry/terrain-mesh.test.ts | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tests/geometry/terrain-mesh.test.ts b/tests/geometry/terrain-mesh.test.ts
index e5b28458..d603c739 100644
--- a/tests/geometry/terrain-mesh.test.ts
+++ b/tests/geometry/terrain-mesh.test.ts
@@ -56,11 +56,19 @@ function collectTopEdgeKeys(options: {
       options.level.positions[positionOffset + varyingOffset]! /
       options.terrain.cellSize;
     const roundedVaryingSample = Math.round(varyingSample);
+    const maxVaryingSample =
+      options.axis === "x"
+        ? options.terrain.sampleCountZ - 1
+        : options.terrain.sampleCountX - 1;
 
     if (Math.abs(varyingSample - roundedVaryingSample) > epsilon) {
       continue;
     }
 
+    if (roundedVaryingSample === 0 || roundedVaryingSample === maxVaryingSample) {
+      continue;
+    }
+
     const sampleX =
       options.axis === "x"
         ? options.sampleCoordinate