junit java單元測試測試多線程并發方法

下面方法摘錄自 http://www.planetgeek.ch/2009/08/25/how-to-find-a-concurrency-bug-with-java/， 用來測試多線程并發執行的方法。

public static void assertConcurrent(final String message, final List<? extends Runnable> runnables, final int maxTimeoutSeconds) throws InterruptedException {
  final int numThreads = runnables.size();
  final List<Throwable> exceptions = Collections.synchronizedList(new ArrayList<Throwable>());
  final ExecutorService threadPool = Executors.newFixedThreadPool(numThreads);
  try {
    final CountDownLatch allExecutorThreadsReady = new CountDownLatch(numThreads);
    final CountDownLatch afterInitBlocker = new CountDownLatch(1);
    final CountDownLatch allDone = new CountDownLatch(numThreads);
    for (final Runnable submittedTestRunnable : runnables) {
      threadPool.submit(new Runnable() {
        public void run() {
          allExecutorThreadsReady.countDown();
          try {
            afterInitBlocker.await();
            submittedTestRunnable.run();
          } catch (final Throwable e) {
            exceptions.add(e);
          } finally {
            allDone.countDown();
          }
        }
      });
    }
    // wait until all threads are ready
    assertTrue("Timeout initializing threads! Perform long lasting initializations before passing runnables to assertConcurrent", 
        allExecutorThreadsReady.await(runnables.size() * 10, TimeUnit.MILLISECONDS));
    // start all test runners
    afterInitBlocker.countDown();
    assertTrue(message +" timeout! More than " + maxTimeoutSeconds + " seconds", allDone.await(maxTimeoutSeconds, TimeUnit.SECONDS));
  } finally {
    threadPool.shutdownNow();
  }
  assertTrue(message + " failed with exception(s) " + exceptions, exceptions.isEmpty());
}

此方法接受三個參數：分別為錯誤消息， 并發執行的Runner列表，以及并發執行的超時時間。

方法中會啟用一個線程池， 并將參數中的所有的Runner都準備好后并發執行runner方法， 并將所有的執行異常存放在一個list中， 如果方法在規定時間內執行完， 并且異常列表為空的情況認為方法正確執行。