model.addTest(new CircleStress());
model.addTest(new DominoTower());
// more interactive..
model.addCategory("Interactive");
model.addTest(new VerticalStack());
model.addTest(new Breakable());
model.addTest(new ShapeEditing());
model.addTest(new OneSidedTest());
model.addTest(new PolyShapes());
model.addTest(new BodyTypes());