public void testStart() throws NoSuchFieldException, IllegalAccessException {

    //checks before starting
    assertFalse(systemProducer.isStarted());

    //start and check if start has been done successfully
    coordinatorStreamWriter.start();
    assertTrue(systemProducer.isStarted());

  }
This class is a unit test for the CoordinatorStreamWriter class.
samza-core/src/test/java/org/apache/samza/coordinator/stream/TestCoordinatorStreamWriter.java