### Question:
StatisticsCounters implements StatisticsHandler { public Counter getCounter(CounterEventTypes counterEventKey) { if (counterEventKey == null) { throw new IllegalArgumentException("counterEventKey can not be null"); } return countersMap.get(counterEventKey); } private  StatisticsCounters(); static synchronized StatisticsCounters getInstance(); void startCounting(boolean reportToLogs, int logReportDelay); void stopCounting(); boolean isRunCounting(); void startLogReport(int logReportDelay); void stopLogReport(); boolean isRunLogReport(); int getLogReportPeriod(); boolean isCounterEnabled(CounterEventTypes counterEventKey); Counter getCounter(CounterEventTypes counterEventKey); void incrementCounter(CounterEventTypes counterEventKey); @Override void resetCounters(); @Override String printStatistics(); static final int DEFAULT_LOG_REPORT_PERIOD; static final int MINIMAL_LOG_REPORT_PERIOD; }### Answer:
@Test(expected = IllegalArgumentException.class) public void testGetCounterbyNull(){ statCounters.getCounter(null); }