如何使用RxJava验证输入?

我的解决办法是 .mergeWith(Observable.just("")) txtInputChangesObservable 现在呢 subscribe{ }

@Test
fun textObs(){
    val submitButtonClickObservable = Observable.just(Any(), Any())
    val txtInputChangesObservable = Observable.empty<CharSequence>()
            .mergeWith(Observable.just(""))
    val testObserver = submitButtonClickObservable
            .withLatestFrom(txtInputChangesObservable).test()
    testObserver.assertValueCount(2)
}