return "";
                case FessConfig.INDEX_ADMIN_DOUBLE_FIELDS:
                    return "";
                case FessConfig.INDEX_ADMIN_DATE_FIELDS:
                    return "expires,start_time,end_time";
                case FessConfig.INDEX_ADMIN_REQUIRED_FIELDS:
                    return "url,title,role,boost";
                case FessConfig.INDEX_ADMIN_ARRAY_FIELDS:
                    return "alerts,roles";

            }
        });
        testThread.start();

        long startTime = System.currentTimeMillis();
        method.invoke(crawler, testThread);
        long endTime = System.currentTimeMillis();

        assertTrue("Thread should have been joined", endTime - startTime >= 100);
    }

    // Test destroyContainer private static method via reflection
    public void test_destroyContainer() throws Exception {