unit-testing - 如何测试观察者？

Question

我会这样测试主持人:

class MostPopularPresenter @Inject constructor(val mostPopularUseCase: MostPopularUseCase) 
: Presenter<MostPopularView>() {

    fun requestMostPopular(page: Int, update: Boolean) {
        if (page <= 6)
            mostPopularUseCase.execute(MostPopularObserver(), MostPopularUseCase.Params.createQuery(page, 15, update))
    }

    inner class MostPopularObserver : DisposableSingleObserver<MostPopularModel>() {

        override fun onSuccess(t: MostPopularModel) {
            this@MostPopularPresenter.view?.populateRecyclerList(t)
        }

        override fun onError(e: Throwable) {
            this@MostPopularPresenter.view?.showError()
        }
    }
}

我有一个问题，如何 mock 观察者，并迫使它在成功时抛出错误或返回值。我正在使用模拟/ junit。有人可以指出我该如何实现吗？也许我的代码无法测试？

Answer 1

observer是一个不应真正测试的对象。虽然有人说，出于某种原因，您还应该测试第三方库，以确保它不会破坏您的代码，但是它已经由第三方开发人员进行了测试。版本之间。

因此，如果您不测试observer ...您如何测试代码？简而言之，您真正需要测试的是演示者本身。在observer内部运行的代码是演示者的一部分。因此，与其模拟observer 而不是模拟useCase:

test useCaseFails() {
    val usecase = // mock use case
    when(usecase.execute(...))
        .thenAnswer(/* receive the observer as first parameter
                       and make it emit an error */)
    val presenter = ...
    presenter.requestMostPopular(...)
    // assert that presenter.view?.showError has been called
}

另一种方法(至少这是我通常的编码方式)是使useCase返回observable并在presenter中订阅它:

class MostPopularPresenter @Inject constructor(val mostPopularUseCase: MostPopularUseCase) 
    : Presenter<MostPopularView>() {

    private var lateinit observer : Disposable

    fun requestMostPopular(page: Int, update: Boolean) {
        if (page <= 6)
            disposable = mostPopularUseCase.execute(MostPopularUseCase.Params.createQuery(page, 15, update))
                .subscribe(t -> view?.populateRecyclerList(t),
                           e -> view?.showError())
    }
}

这样，您可以轻松模拟useCase，从而返回可以控制的Subject:

test useCaseFails() {
    val usecase = // mock use case
    val subject = PublishSubject()
    when(usecase.execute(...))
        .thenReturn(subject)
    val presenter = ...
    presenter.requestMostPopular(...)
    subject.emitError(...) // <- pseudocode
    // assert that presenter.view?.showError has been called
}