### Question:
RequestPathMetricsCollector { public void start() { if (!enabled) { return; } LOG.info("Start the RequestPath collector"); immutableRequestsMap.forEach((opType, pathStatsQueue) -> pathStatsQueue.start()); scheduledExecutor.scheduleWithFixedDelay(() -> { LOG.info("%nHere are the top Read paths:"); logTopPaths(aggregatePaths(4, queue -> !queue.isWriteOperation()), entry -> LOG.info("{} : {}", entry.getKey(), entry.getValue())); LOG.info("%nHere are the top Write paths:"); logTopPaths(aggregatePaths(4, queue -> queue.isWriteOperation()), entry -> LOG.info("{} : {}", entry.getKey(), entry.getValue())); }, COLLECTOR_INITIAL_DELAY, COLLECTOR_DELAY, TimeUnit.MINUTES); } RequestPathMetricsCollector();  RequestPathMetricsCollector(boolean accurateMode); void shutdown(); void start(); void registerRequest(int type, String path); void dumpTopRequestPath(PrintWriter pwriter, String requestTypeName, int queryMaxDepth); void dumpTopReadPaths(PrintWriter pwriter, int queryMaxDepth); void dumpTopWritePaths(PrintWriter pwriter, int queryMaxDepth); void dumpTopPaths(PrintWriter pwriter, int queryMaxDepth); static final String PATH_STATS_SLOT_CAPACITY; static final String PATH_STATS_SLOT_DURATION; static final String PATH_STATS_MAX_DEPTH; static final String PATH_STATS_SAMPLE_RATE; static final String PATH_STATS_COLLECTOR_INITIAL_DELAY; static final String PATH_STATS_COLLECTOR_DELAY; static final String PATH_STATS_TOP_PATH_MAX; static final String PATH_STATS_ENABLED; }### Answer:
@Test public void testCollectEmptyStats() throws InterruptedException { RequestPathMetricsCollector requestPathMetricsCollector = new RequestPathMetricsCollector(); RequestPathMetricsCollector.PathStatsQueue pathStatsQueue = requestPathMetricsCollector.new PathStatsQueue(getChildren); Thread.sleep(5000); Map<String, Integer> newSlot = pathStatsQueue.mapReducePaths(3, pathStatsQueue.getCurrentSlot()); assertTrue(newSlot.isEmpty()); pathStatsQueue.start(); Thread.sleep(15000); newSlot = pathStatsQueue.collectStats(1); assertTrue(newSlot.size() == 0); newSlot = pathStatsQueue.collectStats(2); assertTrue(newSlot.size() == 0); newSlot = pathStatsQueue.collectStats(5); assertTrue(newSlot.size() == 0); }