test: pin chunk mesher vertex layout with exact float count

VoxelEngine.Tests/ChunkMesherTests.cs

@@ -5,7 +5,9 @@ namespace VoxelEngine.Tests;
 
 public class ChunkMesherTests
 {
-    private const int FloatsPerFace = 36; // 6 verts * 6 floats
+    private const int FloatsPerVertex = 6; // pos.xyz, uv, shade
+    private const int VerticesPerFace = 6; // quad = 2 triangles
+    private const int FloatsPerFace = FloatsPerVertex * VerticesPerFace; // 36
 
     private static int FaceCount(float[] mesh) => mesh.Length / FloatsPerFace;
 
@@ -43,13 +45,15 @@ public class ChunkMesherTests
     }
 
     [Fact]
-    public void EveryVertexHasSixFloats()
+    public void SingleBlock_EmitsExactInterleavedFloatCount()
     {
         var chunk = new Chunk();
-        chunk[0, 0, 0] = 1;
+        chunk[0, 0, 0] = 1; // corner block: all 6 neighbors are air/out-of-bounds -> 6 faces
 
         var mesh = new ChunkMesher().Build(chunk, new BlockRegistry());
 
-        Assert.Equal(0, mesh.Length % 6);
+        // Pins the layout: 6 faces * 6 vertices/face * 6 floats/vertex.
+        Assert.Equal(6 * VerticesPerFace * FloatsPerVertex, mesh.Length);
+        Assert.Equal(0, mesh.Length % FloatsPerVertex);
     }
 }