def testLinksReplacement(self):
w = World()
bulb = RyRxJoint(name='bulb')
stem = Body(name='stem', mass=eye(6)*0.1)
w.add_link(w.ground, bulb, stem)
new_bulb = RzRxJoint(name='bulb')
w.replace_joint(bulb, new_bulb) # By another joint
joints = w.getjoints()
self.assertEqual(len(joints), 1)
self.assertEqual(joints[0], new_bulb)
new_new_bulb = RzRyRxJoint(name='bulb')
w.replace_joint(new_bulb, w.ground, new_new_bulb, stem) # By a kinematic chain
joints = w.getjoints()
self.assertEqual(len(joints), 1)
self.assertEqual(joints[0], new_new_bulb)
