change position x,y type + method is_valid and test for move robot

src/main.rs

@@ -32,8 +32,19 @@ impl World {
 
 /// Struct to store robot position.
 struct Position {
-    x: u32,
-    y: u32,
+    x: i32,
+    y: i32,
+}
+
+impl Position {
+    /// Check if position is in the map.
+    fn is_valid(self, w: World) -> Result<(), String> {
+        if (self.x, self.y) > (0, 0) && (self.x, self.y) < (w.x as i32, w.y as i32) {
+            Ok(())
+        } else {
+            Err(String::from("Invalid position."))
+        }
+    }
 }
 
 /// A Robot *aka droid* is represented here.
@@ -257,6 +268,22 @@ mod tests {
         assert_eq!(w.map, vec!['↑', '.', '.', '.']);
     }
 
+    #[test]
+    fn test_move_robot() {
+        let mut r: Robot = Robot {
+            id: 0,
+            o: Orientation::N,
+            p: Position { x: 1, y: 1 },
+            q: Queue::new(),
+        };
+        r.move_forward();
+        assert_eq!(0, r.p.y);
+        r.move_right();
+        assert_eq!(2, r.p.x);
+        r.move_left();
+        assert_eq!(1, r.p.x);
+    }
+
     #[test]
     fn test_empty_position() {
         let mut w: World = World {