Fix tests after recent refactor

rtchallenge/src/canvas.rs

@@ -72,13 +72,13 @@ impl Canvas {
 }
 #[cfg(test)]
 mod tests {
-    use super::canvas;
+    use super::Canvas;
 
     use crate::tuples::Color;
 
     #[test]
     fn create_canvas() {
-        let c = canvas(10, 20);
+        let c = Canvas::new(10, 20);
         assert_eq!(c.width, 10);
         assert_eq!(c.height, 20);
         let black = Color::new(0., 0., 0.);
@@ -89,7 +89,7 @@ mod tests {
 
     #[test]
     fn write_to_canvas() {
-        let mut c = canvas(10, 20);
+        let mut c = Canvas::new(10, 20);
         let red = Color::new(1., 0., 0.);
         c.set(2, 3, red);
         assert_eq!(c.get(2, 3), red);