public void testCall(RxTransaction rxTx) { Observable<String> observable = rxTx.call(new Callable<String>() { @Override public String call() { TestEntity entity = insertEntity("hello"); entity.setSimpleString("world"); daoSession.update(entity); return "Just checking"; } }); TestSubscriber<String> testSubscriber = assertTxExecuted(observable); assertEquals("Just checking", testSubscriber.getOnNextEvents().get(0)); }