class MyPresenter(val api: Api, val view: MyView) {
  fun onSubmitClick() {
    api.submit().subscribe(
      onNext = { data -> view.showSuccess(data) },
      onError = { throwable -> view.showErrorDialog(throwable) }
    )
  }
}

fun testMyPresenterOnSubmitFail() {
  val view: MyView = mock()
  val mockApi: Api = mock {
    // จัดฉาก
    on(it.submit()).thenReturn(Observable.error(Throwable()))
  }
  val presenter = MyPresenter(mockApi, view)

  presenter.onSubmitClick()
  // วัดผล
  verify(view).showErrorDialog(any())
}