ProducerListeners listeners() {
        return new ProducerListeners(eventListeners.toArray(new HollowProducerEventListener[0]));
    }
@Test
    public void testDuplicates() {
        ProducerListenerSupport ls = new ProducerListenerSupport();
        CycleListener l = Mockito.mock(CycleListener.class);
        ls.addListener(l);
        ls.addListener(l);

        ProducerListenerSupport.ProducerListeners s = ls.listeners();
        s.fireCycleStart(1);

        Mockito.verify(l, Mockito.times(1)).onCycleStart(1);
    }