diff --git a/rtiow/renderer/src/bvh_triangles.rs b/rtiow/renderer/src/bvh_triangles.rs
index 4775d8d..6ba1434 100644
--- a/rtiow/renderer/src/bvh_triangles.rs
+++ b/rtiow/renderer/src/bvh_triangles.rs
@@ -183,7 +183,7 @@ where
 
                     let v0v1 = v1 - v0;
                     let v0v2 = v2 - v0;
-                    let normal = cross(v0v1, v0v2);
+                    let normal = cross(v0v1, v0v2).unit_vector();
                     return Some(HitRecord {
                         t,
                         uv,
@@ -289,3 +289,64 @@ fn ray_triangle_intersect_moller_trumbore(r: Ray, tri: &Triangle) -> Option<RayT
     }
     None
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{
+        bvh_triangles::BVHTriangles, cuboid::Cuboid, hitable::Hit, material::Dielectric, ray::Ray,
+    };
+    use std::{
+        io::{BufReader, Cursor},
+        sync::Arc,
+    };
+    use stl::STL;
+
+    #[test]
+    fn compare_cuboid() {
+        let c = Cuboid::new(
+            [0., 0., 0.].into(),
+            [20., 20., 20.].into(),
+            Arc::new(Dielectric::new(1.5)),
+        );
+        let stl_cube = STL::parse(
+            BufReader::new(Cursor::new(include_bytes!("../stls/cube.stl"))),
+            false,
+        )
+        .expect("failed to parse cube");
+
+        let s = BVHTriangles::new(
+            &stl_cube,
+            Dielectric::new(1.5),
+            //Metal::new(Vec3::new(0.8, 0.8, 0.8), 0.2),
+            //Lambertian::new(ConstantTexture::new(Vec3::new(1.0, 0.2, 0.2))),
+        );
+        let rays = [
+            Ray::new([-1., 1., 1.], [1., 0., 0.], 0.),
+            Ray::new([21., 1., 1.], [-1., 0., 0.], 0.),
+            Ray::new([1., -1., 1.], [0., 1., 0.], 0.),
+            Ray::new([1., 21., 1.], [0., -1., 0.], 0.),
+            Ray::new([1., 1., -1.], [0., 0., 1.], 0.),
+            Ray::new([1., 1., 21.], [0., 0., -1.], 0.),
+            // TODO more
+        ];
+
+        for (i, r) in rays.into_iter().enumerate() {
+            let c_hit = c.hit(r, 0., f32::MAX).expect("c_hit missed");
+            let s_hit = s.hit(r, 0., f32::MAX).expect("s_hit missed");
+            assert_eq!(
+                c_hit.t, s_hit.t,
+                "{i}: [t] c_hit: {c_hit:?}, s_hit: {s_hit:?}"
+            );
+            // uv isn't valid for BVHTriangles.
+            // assert_eq!( c_hit.uv, s_hit.uv, "{i}: [uv] c_hit: {c_hit:?}, s_hit: {s_hit:?}");
+            assert_eq!(
+                c_hit.p, s_hit.p,
+                "{i}: [p] c_hit: {c_hit:?}, s_hit: {s_hit:?}"
+            );
+            assert_eq!(
+                c_hit.normal, s_hit.normal,
+                "{i}: [normal] c_hit: {c_hit:?}, s_hit: {s_hit:?}"
+            );
+        }
+    }
+}