Rect in primitives, collect the tests

There's the rectangle!

Also the tests. Cargo doesn't complain, but my YcmCompleter (so
rust-analyze, I think) does. The tests are all one big slab again.

src/main.rs

@@ -5,7 +5,7 @@ mod material;
 mod hittable;
 mod thread_utils;
 
-use crate::primitives::{Vec3, Ray};
+use crate::primitives::{Vec3, Ray, Rect};
 use crate::hittable::Hittable;
 use crate::material::Material;
 use crate::camera::Camera;
@@ -176,14 +176,6 @@ fn sample_pixel(x: i32, y: i32, small_rng: &mut SmallRng, context: &RenderContex
     )
 }
 
-#[derive (Copy, Clone)]
-struct Rect {
-    x: i32,
-    y: i32,
-    w: i32,
-    h: i32,
-}
-
 /* Iterable that produces pixels left-to-right, top-to-bottom.
  * `Tile`s represent the render space, not the finished image.
  * There is no internal pixel buffer

src/primitives.rs

@@ -288,6 +288,26 @@ impl Display for Vec3 {
 	}
 }
 
+#[derive(Copy, Clone)]
+pub struct Ray{
+    pub orig: Vec3,
+    pub dir: Vec3,
+}
+
+impl Ray{
+    pub fn at(&self, t: f32) -> Vec3 {
+        self.orig + self.dir*t
+    }
+}
+
+#[derive (Copy, Clone)]
+pub struct Rect {
+    pub x: i32,
+    pub y: i32,
+    pub w: i32,
+    pub h: i32,
+}
+
 #[cfg(test)]
 mod test{
     use super::*;
@@ -547,23 +567,6 @@ mod test{
         eprintln!("Diff: {}", diff);
         assert!(Vec3::near_zero(&diff));
     }
-}
-
-#[derive(Copy, Clone)]
-pub struct Ray{
-    pub orig: Vec3,
-    pub dir: Vec3,
-}
-
-impl Ray{
-    pub fn at(&self, t: f32) -> Vec3 {
-        self.orig + self.dir*t
-    }
-}
-
-#[cfg(test)]
-mod test{
-    use super::*;
 
     #[test]
     fn check_lerp(){