final SimpleFooEventHandler<SimpleFooProxy> handler =
new SimpleFooEventHandler<SimpleFooProxy>();
EntityProxyChange.registerForProxyType(req.getEventBus(), SimpleFooProxy.class, handler);
SimpleFooRequest context = simpleFooRequest();
final SimpleFooProxy foo = context.create(SimpleFooProxy.class);
final EntityProxyId<SimpleFooProxy> futureId = foo.stableId();
assertTrue(((SimpleEntityProxyId<?>) futureId).isEphemeral());
Request<SimpleFooProxy> fooReq = context.persistAndReturnSelf().using(foo);
fooReq.fire(new Receiver<SimpleFooProxy>() {