### Question:
EngineIoServerOptions { public EngineIoServerOptions setInitialPacket(Packet<?> initialPacket) throws IllegalStateException, IllegalArgumentException { if (mIsLocked) { throw new IllegalStateException("Initial packet cannot be set. Instance is locked."); } if (initialPacket != null) { if ((initialPacket.type == null) || !initialPacket.type.equals(Packet.MESSAGE)) { throw new IllegalArgumentException("Initial packet must be a message packet."); } if (initialPacket.data == null) { throw new IllegalArgumentException("Initial packet data must not be null."); } } mInitialPacket = null; if (initialPacket != null) { mInitialPacket = new Packet<>(initialPacket.type); mInitialPacket.data = initialPacket.data; } return this; } private  EngineIoServerOptions(); static EngineIoServerOptions newFromDefault(); boolean isCorsHandlingDisabled(); EngineIoServerOptions setCorsHandlingDisabled(boolean corsHandlingDisabled); long getPingInterval(); EngineIoServerOptions setPingInterval(long pingInterval); long getPingTimeout(); EngineIoServerOptions setPingTimeout(long pingTimeout); String[] getAllowedCorsOrigins(); EngineIoServerOptions setAllowedCorsOrigins(String[] allowedCorsOrigins); Packet<?> getInitialPacket(); EngineIoServerOptions setInitialPacket(Packet<?> initialPacket); void lock(); int getMaxTimeoutThreadPoolSize(); EngineIoServerOptions setMaxTimeoutThreadPoolSize(int maxTimeoutThreadPoolSize); static final EngineIoServerOptions DEFAULT; static final String[] ALLOWED_CORS_ORIGIN_ALL; static final String[] ALLOWED_CORS_ORIGIN_NONE; }### Answer:
@Test(expected = IllegalStateException.class) public void testDefaultLocked4() { EngineIoServerOptions.DEFAULT.setInitialPacket(null); }