The test case below is about a single add - probably more issues with other modifications of underlying list, too lazy to go for a hunt

    /**
     * Change incorrect on add.
     */
    @Test
    public void testFilteredNotificationAdd() {
        ObservableList<Integer> original = FXCollections.observableArrayList(
                0, 1, 2, 3, 4 ,5, 6, 7, 8, 9
        );
        FilteredList list = new FilteredList(original, new Always());
        final ObjectProperty<Change> change = new ObjectProperty<Change>();
        ListChangeListener l = new ListChangeListener() {

            @Override
            public void onChanged(Change c) {
                change.set(c);
            }
            
        };
        list.addListener(l);
        original.add(20);
        assertEquals("from", list.size() - 1, change.get().getFrom());
        assertEquals("to", list.size(), change.get().getTo());
        assertEquals("added", true, change.get().wasAdded());
}