@Override
    public void close() {
      LOG.info("Task instance is shutting down.");
      shutdownLatch.countDown();
    }
A test TaskApplication to use in test harnesses.
@param systemName test input/output system
@param inputTopic topic to consume
@param outputTopic topic to output
@param processedMessageLatch latch that counts down per message processed
@param shutdownLatch latch that counts down once during shutdown
@param processCallback optional callback called per message processed.
samza-test/src/test/java/org/apache/samza/test/processor/TestTaskApplication.java