added and reorganized unit tests for BasicQueueTest and QueueListenerTest

I would use a @Test(expected=NullPointerException.class)

If you want to use the try/catch (which is also fine), make sure you do a 

```
try{
 your operation thatis going to throw npe
  fail()
}catch(NullPointerException expected){
}
```

If you don't add fail, you don't see if the NPE is not thrown.