### Question:
TransactionManager extends QBeanSupport implements Runnable, TransactionConstants, TransactionManagerMBean, Loggeable, MetricsProvider { @Override public void startService () throws Exception { NameRegistrar.register(getName(), this); recover(); threads = Collections.synchronizedList(new ArrayList(maxSessions)); if (tps != null) tps.stop(); tps = new TPS (cfg.getBoolean ("auto-update-tps", true)); for (int i=0; i<sessions; i++) { new Thread(this).start(); } if (psp.rdp (RETRY_QUEUE) != null) checkRetryTask(); if (maxSessions > sessions) { loadMonitorExecutor = ConcurrentUtil.newScheduledThreadPoolExecutor(); loadMonitorExecutor.scheduleAtFixedRate( new Thread(() -> { int outstandingTransactions = getOutstandingTransactions(); int activeSessions = getActiveSessions(); if (activeSessions < maxSessions && outstandingTransactions > threshold) { int count = Math.min(outstandingTransactions, maxSessions - activeSessions); for (int i=0; i<count; i++) new Thread(this).start(); getLog().info("Created " + count + " additional sessions"); } }), 5, 1, TimeUnit.SECONDS) ; } if (iisp != isp) { new Thread(new InputQueueMonitor()).start(); } }  @Override void initService(); @Override void startService(); @Override void stopService(); void queue(Serializable context); void push(Serializable context); @SuppressWarnings("unused") String getQueueName(); Space getSpace(); Space getInputSpace(); Space getPersistentSpace(); @Override void run(); @Override long getTail(); @Override long getHead(); long getInTransit(); @Override void setConfiguration(Configuration cfg); void addListener(TransactionStatusListener l); void removeListener(TransactionStatusListener l); TPS getTPS(); @Override String getTPSAsString(); @Override float getTPSAvg(); @Override int getTPSPeak(); @Override Date getTPSPeakWhen(); @Override long getTPSElapsed(); @Override void resetTPS(); @Override Metrics getMetrics(); @Override void dump(PrintStream ps, String indent); TransactionParticipant createParticipant(Element e); @Override int getOutstandingTransactions(); @Override void setDebug(boolean debug); @Override boolean getDebugContext(); @Override void setDebugContext(boolean debugContext); @Override boolean getDebug(); @Override int getActiveSessions(); int getPausedCounter(); int getActiveTransactions(); int getMaxSessions(); static Serializable getSerializable(); static T getContext(); static Long getId(); static final String HEAD; static final String TAIL; static final String CONTEXT; static final String STATE; static final String GROUPS; static final String TAILLOCK; static final String RETRY_QUEUE; static final Integer PREPARING; static final Integer COMMITTING; static final Integer DONE; static final String DEFAULT_GROUP; static final long MAX_PARTICIPANTS; static final long MAX_WAIT; static final long TIMER_PURGE_INTERVAL; }### Answer:
@Test public void testStartServiceThrowsNullPointerException1() throws Throwable { transactionManager.setName("testTransactionManagerName"); try { transactionManager.startService(); fail("Expected NullPointerException to be thrown"); } catch (NullPointerException ex) { if (isJavaVersionAtMost(JAVA_14)) { assertNull(ex.getMessage(), "ex.getMessage()"); } else { assertEquals("Cannot enter synchronized block because \"this.psp\" is null", ex.getMessage(), "ex.getMessage()"); } assertNull(transactionManager.psp, "transactionManager.psp"); assertNull(transactionManager.threads, "transactionManager.threads"); assertNull(transactionManager.getConfiguration(), "transactionManager.getConfiguration()"); assertEquals(0L, transactionManager.tail, "transactionManager.tail"); assertNull(transactionManager.groups, "transactionManager.groups"); } }