ShutdownListener listener = new ShutdownListener() {
            @Override
            public void onShutdown() {
                shutdownCalled.set(true);
            }
        };

        jobExecutor.addShutdownListener(listener);
        assertNotNull(jobExecutor.shutdownListener);
        assertEquals(listener, jobExecutor.shutdownListener);

     */
    public void shutdown() {
        shutdownListener.onShutdown();
    }

    /**
     * Adds a shutdown listener to be notified when the executor is shutting down.
     *
     * @param listener the shutdown listener to add
     */
    public void addShutdownListener(final ShutdownListener listener) {
        shutdownListener = listener;
    }

    /**