Small Test for metrics library

MetricsTest.java

package com.velogica.metrics;

import com.codahale.metrics.*;
import com.codahale.metrics.jvm.GarbageCollectorMetricSet;
import com.codahale.metrics.jvm.MemoryUsageGaugeSet;
import com.codahale.metrics.jvm.ThreadStatesGaugeSet;
import org.junit.Test;

import rx.Observable;
import rx.functions.Action1;

import java.util.Map;
import java.util.concurrent.TimeUnit;

import static org.junit.Assert.*;


/**
 * https://dropwizard.github.io/metrics/3.1.0/getting-started/
 * Created by usunoda on 4/28/2015.
 */


public class MetricsTest {

    static final MetricRegistry metrics = new MetricRegistry();

    @Test
    public void testBasicMetrics() {

        ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics)
                .convertRatesTo(TimeUnit.SECONDS)
                .convertDurationsTo(TimeUnit.MILLISECONDS)
                .build();
        reporter.start(1, TimeUnit.SECONDS);
        Meter requests = metrics.meter("requests");
        requests.mark();
        try {
            Thread.sleep(5 * 1000);
        } catch (InterruptedException e) {
            fail("exception sleeping");
        }
        requests.mark();
        assertTrue(true);

    }

    @Test
    public void testJVMMetrics() {

        ConsoleReporter reporter = ConsoleReporter.forRegistry(metrics)
                .convertRatesTo(TimeUnit.SECONDS)
                .convertDurationsTo(TimeUnit.MILLISECONDS)
                .build();
        reporter.start(1, TimeUnit.SECONDS);

        checkMetricSet(new GarbageCollectorMetricSet());

        System.out.println("\n\n=== Memory Metrics ===\n\n");

        checkMetricSet(new MemoryUsageGaugeSet());
        byte[] largeByteArray = new byte[100000000];
        checkMetricSet(new MemoryUsageGaugeSet());

        System.out.println("\n\n=== Thread Metrics ===\n\n");

        checkMetricSet(new ThreadStatesGaugeSet());

    }

    protected void checkMetricSet(MetricSet metricSet) {
        for(Map.Entry<String, Metric> metricEntry: metricSet.getMetrics().entrySet()) {
            assertNotNull(metricEntry.getValue());
            if (metrics.getGauges().get("test." + metricEntry.getKey()) == null) {
                metrics.register("test." + metricEntry.getKey(), metricEntry.getValue());
            }
        }

        for (Map.Entry<String, Metric> metricEntry: metricSet.getMetrics().entrySet()) {
            String metricName = "test." + metricEntry.getKey();
            System.out.print(metricName + " = ");
            Object value = metrics.getGauges().get(metricName).getValue();
            System.out.println(value);
            assertNotNull(value);
        }

    }

}