private static class Always implements Matcher<Integer> {
        
        @Override
        public boolean matches(Integer i) {
            return true;
        }
    }
    
    private static class Never implements Matcher<Integer> {
        
        @Override
        public boolean matches(Integer i) {
            return false;
        }
    }
    
    /**
     * Matcher rejecting all: strange behaviour in batch mode
     */
    @Test
    public void testFilteredKeepNoneBatch() {
        ObservableList<Integer> original = FXCollections.observableArrayList(
                0, 1, 2, 3, 4 ,5, 6, 7, 8, 9
        );
        FilteredList list = new FilteredList(original, new Never(), FilterMode.BATCH);
        list.filter();
        assertEquals("must have null size, matcher rejects all " + list, 0, list.size());
    }

    /**
    * okay if set after some filtering has happened
    */
    @Test
    public void testFilteredBatchChangeMatcher() {
        ObservableList<Integer> original = FXCollections.observableArrayList(
               0, 1, 2, 3, 4 ,5, 6, 7, 8, 9
        );
        FilteredList list = new FilteredList(original, new Always(), FilterMode.BATCH);
        list.filter();
        assertEquals(original.size(), list.size());
        list.setMatcher(new Never());
        list.filter();
        assertEquals(0, list.size());
        
    }

    /**
     * Filter okay in Live mode
     */
    @Test
    public void testFilteredKeepNoneLive() {
        ObservableList<Integer> original = FXCollections.observableArrayList(
                0, 1, 2, 3, 4 ,5, 6, 7, 8, 9
        );
        FilteredList list = new FilteredList(original, new Never());
        assertEquals(0, list.size());
    }