@Test
public void testAddChild() throws Throwable {

  MockService one = new MockService("one", false, 5000);
  MockService two = new MockService("two", false, 100);
  ServiceParent parent = startService(one, two);
  CallableHandler handler = new CallableHandler("hello");
  WorkflowCallbackService<String> ens =
      new WorkflowCallbackService<String>("handler", handler, 100, true);
  parent.addService(ens);
  waitForParentToStop(parent, 10000);
  assertStopped(one);
  assertStopped(two);
  assertStopped(ens);
  assertStopped(two);
  assertEquals("hello", ens.getScheduledFuture().get());
}