assertEquals(4, observerHelper.nbUpdated());
assertEquals(LeafUpdateCode.age, observerHelper.getUpdateObjects().get(0));
assertEquals(LeafUpdateCode.efficiency, observerHelper.getUpdateObjects().get(1));
assertEquals(LeafUpdateCode.energy, observerHelper.getUpdateObjects().get(2));
assertEquals(LeafUpdateCode.fall, observerHelper.getUpdateObjects().get(3));
MockGravity gravity = (MockGravity) universe.getUniverse3D().getPhysics().getGravity();
assertEquals(bg, gravity.getFallenGroup());
}