@Test
  public void testParallelism() throws Exception {
    final MultiVersionConcurrencyControl mvcc = new MultiVersionConcurrencyControl();

    final AtomicBoolean finished = new AtomicBoolean(false);

    // fail flag for the reader thread
    final AtomicBoolean readerFailed = new AtomicBoolean(false);
    final AtomicLong failedAt = new AtomicLong();
    Runnable reader = new Runnable() {
      @Override
      public void run() {
        long prev = mvcc.getReadPoint();
        while (!finished.get()) {
          long newPrev = mvcc.getReadPoint();
          if (newPrev < prev) {
            // serious problem.
            System.out.println("Reader got out of order, prev: " + prev + " next was: " + newPrev);
            readerFailed.set(true);
            // might as well give up
            failedAt.set(newPrev);
            return;
          }
        }
      }
    };

    // writer thread parallelism.
    int n = 20;
    Thread[] writers = new Thread[n];
    AtomicBoolean[] statuses = new AtomicBoolean[n];
    Thread readThread = new Thread(reader);

    for (int i = 0; i < n; ++i) {
      statuses[i] = new AtomicBoolean(true);
      writers[i] = new Thread(new Writer(finished, mvcc, statuses[i]));
      writers[i].start();
    }
    readThread.start();

    try {
      Thread.sleep(10 * 1000);
    } catch (InterruptedException ex) {
    }

    finished.set(true);

    readThread.join();
    for (int i = 0; i < n; ++i) {
      writers[i].join();
    }

    // check failure.
    Assert.assertFalse(readerFailed.get());
    for (int i = 0; i < n; ++i) {
      Assert.assertTrue(statuses[i].get());
    }
  }
This is a hammer test that verifies MultiVersionConcurrencyControl in a multiple writer single
reader scenario.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestMultiVersionConcurrencyControl.java