@Override
    public void output(String text) {
        stringBuilder.append(prefixes.pop()).append(text);
        prefixes.push(", ");
    }
@Test
    public void testOutput() {
        NodeStringifier stringifier = new NodeStringifier();
        stringifier.output("testing 123");
        stringifier.output("again");
        assertEquals("testing 123, again", stringifier.toString());
    }