@Test
  public void testZipfian() throws NoSuchMethodException, SecurityException, InstantiationException,
    IllegalAccessException, IllegalArgumentException, InvocationTargetException {
    TestOptions opts = new PerformanceEvaluation.TestOptions();
    opts.setValueZipf(true);
    final int valueSize = 1024;
    opts.setValueSize(valueSize);
    RandomReadTest rrt = new RandomReadTest(null, opts, null);
    Constructor<?> ctor =
      Histogram.class.getDeclaredConstructor(com.codahale.metrics.Reservoir.class);
    ctor.setAccessible(true);
    Histogram histogram = (Histogram) ctor.newInstance(new UniformReservoir(1024 * 500));
    for (int i = 0; i < 100; i++) {
      histogram.update(rrt.getValueLength());
    }
    Snapshot snapshot = histogram.getSnapshot();
    double stddev = snapshot.getStdDev();
    assertTrue(stddev != 0 && stddev != 1.0);
    assertTrue(snapshot.getStdDev() != 0);
    double median = snapshot.getMedian();
    assertTrue(median != 0 && median != 1 && median != valueSize);
  }
Exercise the mr spec writing. Simple assertions to make sure it is basically working.
hbase-diagnostics/src/test/java/org/apache/hadoop/hbase/TestPerformanceEvaluation.java