rover: wrap when going negative

rover/rover.py

@@ -29,3 +29,8 @@ class Rover(BaseModel):
             self.pos.x += 1
         elif self.dir == Direction.WEST:
             self.pos.x -= 1
+
+        if self.pos.x < 0:
+            self.pos.x += self.planet_size.x
+        if self.pos.y < 0:
+            self.pos.y += self.planet_size.y

rover/test_rover.py

@@ -60,3 +60,19 @@ def test_rover_can_go_forward_going_west():
     )
     rov.forward()
     assert rov.pos == Vector(x=0, y=0)
+
+
+def test_rover_can_wrap_under_north_south():
+    rov = Rover(
+        pos=Vector(x=0, y=0), planet_size=Vector(x=10, y=10), dir=Direction.SOUTH
+    )
+    rov.forward()
+    assert rov.pos == Vector(x=0, y=9)
+
+
+def test_rover_can_wrap_under_east_west():
+    rov = Rover(
+        pos=Vector(x=0, y=0), planet_size=Vector(x=10, y=10), dir=Direction.WEST
+    )
+    rov.forward()
+    assert rov.pos == Vector(x=9, y=0)