    @Test
    public void testAddListener() {

        NeuralNetworkEventListener l = Mockito.mock(NeuralNetworkEventListener.class);
        instance.addListener(l);
        NeuralNetworkEvent event = Mockito.mock(NeuralNetworkEvent.class);
        instance.fireNetworkEvent(event);
        Mockito.verify(l).handleNeuralNetworkEvent(event);

        NeuralNetworkEventListener l1 = Mockito.mock(NeuralNetworkEventListener.class);
        Mockito.verify(l1, Mockito.never()).handleNeuralNetworkEvent(event);
    }