def test_remove_old(self):
Entity.erase_all_entities()
# add and remove an NPC
an_NPC = self.new_NPC()
self.assertNotEquals(Entity.all_NPCs, [])
Entity.remove_old(an_NPC)
self.assertEquals(Entity.all_NPCs, [])
# add and remove a player
a_player = self.new_player()
self.assertNotEquals(Entity.player, None)
Entity.remove_old(a_player)
self.assertEquals(Entity.player, None)
# add and remove an thing
a_thing = self.new_thing()
self.assertNotEquals(Entity.all_things, [])
Entity.remove_old(a_thing)
self.assertEquals(Entity.all_things, [])
