@Test
public void testThatYouCannotBuyIfYouRunOutOfMoney(TestContext tc) {

  Async async = tc.async();
  service.buy(10000, quote("A", 10, 20, 100000), ar -> {
    tc.assertTrue(ar.failed());
    tc.assertTrue(ar.cause().getMessage().contains("not enough money"));
    async.complete();
  });
}