public void testAllowNulls() {
Set<Object> s = new LinkedHashSet<Object>();
s.add("abc");
s.add(null);
s.add("def");
IterableJsonOutputRenderer renderer = new IterableJsonOutputRenderer(true);
JSONStringer jsonWriter = new JSONStringer();
jsonWriter.addRenderer(renderer);
jsonWriter.value(s);
assertEquals(jsonWriter.toString(), "[\"abc\",null,\"def\"]");
}