ListenerRegistration secondReg = router.addAttributeListener(new DummyElm(),
mock(AttributeListener.class));
assertEquals(1, docListeners.size());
firstReg.detach();
assertEquals(1, docListeners.size());
secondReg.detach();
assertEquals(0, docListeners.size());
}
/**
* Test that removing a node removes all associated listeners and, if possible,