Add unit test to dubbo-monitor module
try {
            Monitor monitor = null;
            long start = System.currentTimeMillis();
            while (System.currentTimeMillis() - start < 60000) {
                monitor = monitorFactory.getMonitor(URL.valueOf("dubbo://127.0.0.1:17979?interval=10"));
                if (monitor == null) {
                    continue;
                }
                try {
                    monitor.collect(statistics);
                    int i = 0;
                    while (monitorService.getStatistics() == null && i < 200) {
                        i++;
                        Thread.sleep(10);
                    }
                    URL result = monitorService.getStatistics();
                    Assert.assertEquals(1, result.getParameter(MonitorService.SUCCESS, 0));
                    Assert.assertEquals(3, result.getParameter(MonitorService.ELAPSED, 0));
                } finally {
                    monitor.destroy();
                }
                break;
            }
            Assert.assertNotNull(monitor);
        } finally {
            exporter.unexport();
        }
    }
}