hmm - so we can't access the `worker.running` variable which would be useful for this. Looking at the Gearman worker, there's not much we can do there https://github.com/mikespook/gearman-go/blob/master/worker/worker.go.

Maybe a mocked worker? That is hard in this case as there's not an easy way to pass in a mocked gearman worker:
```
  w := gearmanWorker.New(gearmanWorker.OneByOne)
```

we could mock out `Shutdown` and `Close`, but they are so simple it seems a little crazy.