Oh, and:

```python
q = Queue('first')
r = Queue('second')
s = Queue('third')
self.assertEquals(len(Queue.all()), 0)
q.enqueue_job(...)
self.assertEquals(len(Queue.all()), 1)

# now work
w = Worker([q])
w.work(burst=False)

# Queue.all() should remove the 'first' queue from the list now, as per @selwin's suggestion
self.assertEquals(len(Queue.all()), 0)
```