diff --git a/pong/src/geom.rs b/pong/src/geom.rs
index 2ab8e2c..f25138c 100644
--- a/pong/src/geom.rs
+++ b/pong/src/geom.rs
@@ -135,6 +135,7 @@ pub mod geom {
         }
     }
 
+    #[derive(Clone)]
     pub struct BoundingBox {
         top_left: Vector,
         top_right: Vector,
diff --git a/pong/tests/collision_tests.rs b/pong/tests/collision_tests.rs
index fbf9b99..7e429df 100644
--- a/pong/tests/collision_tests.rs
+++ b/pong/tests/collision_tests.rs
@@ -1,40 +1,41 @@
 use rstest::rstest;
 use pong::collision::collision::{Collision, CollisionDetector};
-use pong::game_object::game_object::{GameObject, ShapeType};
-use pong::geom::geom::{Vector};
+use pong::game_object::game_object::GameObject;
+use pong::geom::geom::{BoundingBox, Vector};
+
 
 #[rstest]
 #[case(vec![], vec![])]
 #[case(
     vec![
-        GameObject{id: 1, pos: Vector{x: 50., y: 50.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)},
-        GameObject{id: 2, pos: Vector{x: 50., y: 50.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)}
+        MockGameObject::new(1, BoundingBox::new(Vector{x: 50., y: 50.}, 20., 20.)),
+        MockGameObject::new(2, BoundingBox::new(Vector{x: 50., y: 50.}, 20., 20.))
     ],
     vec![Collision(1, 2)]
 )]
 #[case(
     vec![
-        GameObject{id: 1, pos: Vector{x: 60., y: 65.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)},
-        GameObject{id: 2, pos: Vector{x: 50., y: 50.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)}
+        MockGameObject::new(1, BoundingBox::new(Vector{x: 60., y: 65.}, 20., 20.)),
+        MockGameObject::new(2, BoundingBox::new(Vector{x: 50., y: 50.}, 20., 20.)),
     ],
     vec![Collision(1, 2)]
 )]
 #[case(
     vec![
-        GameObject{id: 1, pos: Vector{x: 50., y: 50.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)},
-        GameObject{id: 2, pos: Vector{x: 80., y: 80.}, shape: Shape::Rect, shape_params: vec![20, 20], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)}
+        MockGameObject::new(1, BoundingBox::new(Vector{x: 50., y: 50.}, 20., 20.)),
+        MockGameObject::new(2, BoundingBox::new(Vector{x: 80., y: 80.}, 20., 20.)),
     ],
     vec![]
 )]
 #[case(
     vec![
-        GameObject{id: 1, pos: Vector{x: 50., y: 50.}, shape: Shape::Rect, shape_params: vec![50, 50], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)},
-        GameObject{id: 2, pos: Vector{x: 500., y: 50.}, shape: Shape::Rect, shape_params: vec![50, 50], vel: Vector::zero(), is_static: false, orientation: Vector::new(1., 1.)}
+        MockGameObject::new(1, BoundingBox::new(Vector{x: 50., y: 50.}, 50., 50.)),
+        MockGameObject::new(2, BoundingBox::new(Vector{x: 500., y: 50.}, 50., 50.)),
     ],
     vec![]
 )]
 pub fn should_detect_collisions(
-    #[case] objs: Vec<GameObject>,
+    #[case] objs: Vec<Box<dyn GameObject>>,
     #[case] expected_collisions: Vec<Collision>,
 ) {
     let detector = CollisionDetector::new();
@@ -44,3 +45,56 @@ pub fn should_detect_collisions(
         expected_collisions.iter().collect::<Vec<&Collision>>()
     );
 }
+
+#[derive(Debug)]
+pub struct MockGameObject {
+    id: u16,
+    bounding_box: BoundingBox
+}
+
+impl MockGameObject {
+    pub fn new(id: u16, bounding_box: BoundingBox) -> Box<dyn GameObject> {
+        Box::new(
+            MockGameObject {
+                id, bounding_box
+            }
+        )
+    }
+}
+
+impl GameObject for MockGameObject {
+    fn id(&self) -> u16 {
+        self.id
+    }
+
+    fn pos(&self) -> &Vector {
+        &Vector::zero()
+    }
+
+    fn pos_mut(&mut self) -> &mut Vector {
+        &mut Vector::zero()
+    }
+
+    fn orientation(&self) -> &Vector {
+        &Vector::zero()
+    }
+
+    fn update_pos(&mut self) {
+    }
+
+    fn bounding_box(&self) -> BoundingBox {
+        self.bounding_box.clone()
+    }
+
+    fn vel(&self) -> &Vector {
+        &Vector::zero()
+    }
+
+    fn vel_mut(&mut self) -> &mut Vector {
+        &mut Vector::zero()
+    }
+
+    fn is_static(&self) -> bool {
+        return false;
+    }
+}
diff --git a/pong/tests/game_field_test.rs b/pong/tests/game_field_test.rs
index 54ce890..cb85dc6 100644
--- a/pong/tests/game_field_test.rs
+++ b/pong/tests/game_field_test.rs
@@ -14,7 +14,7 @@ mod game_field_tests {
         field.tick(inputs);
         let players = field.players();
         let player = players.first().unwrap();
-        assert_eq!(player.obj.pos.y, height as f64 / 2. + 1.);
+        assert_eq!(player.obj.pos().y, height as f64 / 2. + 1.);
     }
 
     #[test]
@@ -29,7 +29,7 @@ mod game_field_tests {
         field.tick(inputs);
         let players = field.players();
         let player = players.first().unwrap();
-        assert_eq!(player.obj.pos.y, height as f64 / 2. - 1.);
+        assert_eq!(player.obj.pos().y, height as f64 / 2. - 1.);
     }
 
     #[test]
@@ -44,7 +44,7 @@ mod game_field_tests {
         field.tick(inputs);
         let players = field.players();
         let player = players.first().unwrap();
-        assert_eq!(player.obj.pos.y, height as f64 - height as f64 / 5. / 2.);
+        assert_eq!(player.obj.pos().y, height as f64 - height as f64 / 5. / 2.);
     }
 
     #[test]
@@ -59,6 +59,6 @@ mod game_field_tests {
         field.tick(inputs);
         let players = field.players();
         let player = players.first().unwrap();
-        assert_eq!(player.obj.pos.y, height as f64 / 5. / 2.);
+        assert_eq!(player.obj.pos().y, height as f64 / 5. / 2.);
     }
 }