@Test
    public void worksWithSeveralFieldFilters() {
        citations.add(c1);
        citations.add(c2);
        citations.add(cnull);
        filter.addFieldFilter("author", "Kekkonen");
        filter.addFieldFilter("author", "Isoherra");
        List<Citation> filtered = filter.getFilteredList();
        List<Citation> expected = new LinkedList<Citation>();
        expected.add(c1);
        expected.add(c2);
        assertTrue(filtered.containsAll(expected) && filtered.size() == 2);
    }