Add rotation unit tests

src/card.rs

@@ -714,11 +714,33 @@ mod test {
 
   #[test]
   fn rotate_clockwise() {
-    todo!();
+    let shape = Card {
+      cells: NW_TRIANGLE,
+      ..Default::default()
+    };
+
+    let expected = Card {
+      cells: NE_TRIANGLE,
+      ..Default::default()
+    };
+
+    let result = shape.rotate(RotationDir::Clockwise);
+    assert_eq!(result, expected);
   }
 
   #[test]
   fn rotate_counter_clockwise() {
-    todo!();
+    let shape = Card {
+      cells: NE_TRIANGLE,
+      ..Default::default()
+    };
+
+    let expected = Card {
+      cells: NW_TRIANGLE,
+      ..Default::default()
+    };
+
+    let result = shape.rotate(RotationDir::CounterClockwise);
+    assert_eq!(result, expected);
   }
 }