diff --git a/rtchallenge/src/transformations.rs b/rtchallenge/src/transformations.rs
index b0963da..e91b5e1 100644
--- a/rtchallenge/src/transformations.rs
+++ b/rtchallenge/src/transformations.rs
@@ -5,47 +5,6 @@ use crate::{
 
 /// Create a matrix representing a eye at `from` looking at `to`, with an `up`
 /// as the up vector.
-///
-/// # Examples
-/// ```
-/// use rtchallenge::{matrices::Matrix4x4, transformations::view_transform, tuples::Tuple};
-///
-/// // The transofrmation matrix for the default orientation.
-/// let from = Tuple::point(0., 0., 0.);
-/// let to = Tuple::point(0., 0., -1.);
-/// let up = Tuple::vector(0., 1., 0.);
-/// let t = view_transform(from, to, up);
-/// assert_eq!(t, Matrix4x4::identity());
-///
-/// // A view transformation matrix looking in positive z direction.
-/// let from = Tuple::point(0., 0., 0.);
-/// let to = Tuple::point(0., 0., 1.);
-/// let up = Tuple::vector(0., 1., 0.);
-/// let t = view_transform(from, to, up);
-/// assert_eq!(t, Matrix4x4::scaling(-1., 1., -1.));
-///
-/// // The view tranformation moves the world.
-/// let from = Tuple::point(0., 0., 8.);
-/// let to = Tuple::point(0., 0., 0.);
-/// let up = Tuple::vector(0., 1., 0.);
-/// let t = view_transform(from, to, up);
-/// assert_eq!(t, Matrix4x4::translation(0., 0., -8.));
-///
-/// // An arbitrary view transformation.
-/// let from = Tuple::point(1., 3., 2.);
-/// let to = Tuple::point(4., -2., 8.);
-/// let up = Tuple::vector(1., 1., 0.);
-/// let t = view_transform(from, to, up);
-/// assert_eq!(
-///     t,
-///     Matrix4x4::new(
-///         [-0.50709, 0.50709, 0.67612, -2.36643],
-///         [0.76772, 0.60609, 0.12122, -2.82843],
-///         [-0.35857, 0.59761, -0.71714, 0.],
-///         [0., 0., 0., 1.],
-///     )
-/// );
-/// ```
 pub fn view_transform(from: Tuple, to: Tuple, up: Tuple) -> Matrix4x4 {
     let forward = (to - from).normalize();
     let left = cross(forward, up.normalize());
@@ -57,3 +16,56 @@ pub fn view_transform(from: Tuple, to: Tuple, up: Tuple) -> Matrix4x4 {
         [0., 0., 0., 1.],
     ) * Matrix4x4::translation(-from.x, -from.y, -from.z)
 }
+
+#[cfg(test)]
+mod tests {
+    use crate::{
+        matrices::{identity, scaling, translation, Matrix4x4},
+        transformations::view_transform,
+        tuples::{point, vector},
+    };
+    #[test]
+    fn default_orientation() {
+        // The transformation matrix for the default orientation.
+        let from = point(0., 0., 0.);
+        let to = point(0., 0., -1.);
+        let up = vector(0., 1., 0.);
+        let t = view_transform(from, to, up);
+        assert_eq!(t, identity());
+    }
+    #[test]
+    fn looking_positive_z() {
+        // A view transformation matrix looking in positive z direction.
+        let from = point(0., 0., 0.);
+        let to = point(0., 0., 1.);
+        let up = vector(0., 1., 0.);
+        let t = view_transform(from, to, up);
+        assert_eq!(t, scaling(-1., 1., -1.));
+    }
+    #[test]
+    fn transformation_moves_world() {
+        // The view transformation moves the world.
+        let from = point(0., 0., 8.);
+        let to = point(0., 0., 0.);
+        let up = vector(0., 1., 0.);
+        let t = view_transform(from, to, up);
+        assert_eq!(t, translation(0., 0., -8.));
+    }
+    #[test]
+    fn arbitrary_view() {
+        // An arbitrary view transformation.
+        let from = point(1., 3., 2.);
+        let to = point(4., -2., 8.);
+        let up = vector(1., 1., 0.);
+        let t = view_transform(from, to, up);
+        assert_eq!(
+            t,
+            Matrix4x4::new(
+                [-0.50709, 0.50709, 0.67612, -2.36643],
+                [0.76772, 0.60609, 0.12122, -2.82843],
+                [-0.35857, 0.59761, -0.71714, 0.],
+                [0., 0., 0., 1.],
+            )
+        );
+    }
+}