JUnit 5测试-无法观察嵌套的LiveData值

Question

概述

Expected-将嵌套的LiveData值保存在本地单元测试中，然后声明它们的值。

Observed-在生产代码中成功观察到将嵌套LiveData值保存在ViewModel中，但是在本地单元测试中失败。这可能是由于本地单元测试与在Android环境上运行相比缺少线程。

代码

• ViewModel包含用户选择要打开的内容时的LOADING，CONTENT和ERROR（LCE）条件。
• 保存LiveData NotifyItemChangedEffect状态以更新视图。
• NotifyItemChangedEffect保存在函数内部，以保存发送到视图的内容。 仅在CONTENT条件下，所选项目被发送到保存有LiveData对象ContentToPlay的视图。
• 在生产中，这适用于在LOADING，CONTENT和ERROR期间视图的UI更新，而在成功ContentToPlay条件下返回[[only CONTENT。

ContentViewModel.kt

    is ContentSelected -> {
        _feedViewState.value = _feedViewState.value?.copy(

                // LiveData value for ContentToPlay initiated here.
                contentToPlay = switchMap(getAudiocast(contentSelected)) { lce ->
                    liveData {
                        when (lce) {
                            is Loading ->
                                _viewEffect.value = _viewEffect.value?.copy(
                                        notifyItemChanged = liveData {
                                            emit(Event(NotifyItemChangedEffect(...)))
                                        })
                            is Lce.Content -> {
                                _viewEffect.value = _viewEffect.value?.copy(
                                        notifyItemChanged = liveData {
                                            emit(Event(NotifyItemChangedEffect(...)))
                                        })

                                // LiveData value for ContentToPlay saved here.
                                emit(Event(lce.packet))
                            }
                            is Error -> {
                                _viewEffect.value = _viewEffect.value?.copy(
                                        notifyItemChanged = liveData {
                                            emit(Event(NotifyItemChangedEffect(...)))
                                        })
                                _viewEffect.value = _viewEffect.value?.copy(
                                        snackBar = liveData {
                                            emit(Event(SnackBarEffect(...)))
                                        })
                            }
                        }
                    }
                })
        ...
    }

• 通过设计

-在ContentToPlay和LOADING条件下不返回ERROR。

问题

-NotifyItemChangedEffect的嵌套LiveData值未保存在单元测试中，该单元测试会在每个LCE条件下更新视图。该代码在为ContentToPlay保存的LiveData内部执行。该模式已记录并在生产中工作。

PlayContentTests.kt

    @ExtendWith(InstantExecutorExtension::class)
    class PlayContentTests {
        @ParameterizedTest
        @MethodSource("FeedLoad")
        fun `Play Content`(test: PlayContentTest) = runBlocking {
            // ViewModel method included to initiate ContentSelected event.
            ...
            when (test.lceState) {
                LOADING ->
                    assertThat(contentViewModel.viewEffect.getOrAwaitValue().notifyItemChanged.getOrAwaitValue().peekEvent()).isEqualTo(
                            NotifyItemChangedEffect(...))
                CONTENT -> {
                    assertThat(contentViewModel.feedViewState.getOrAwaitValue().contentToPlay.getOrAwaitValue().peekEvent()).isEqualTo(
                            ContentToPlay(...))
                    assertThat(contentViewModel.viewEffect.getOrAwaitValue().notifyItemChanged.getOrAwaitValue().peekEvent()).isEqualTo(
                            NotifyItemChangedEffect(...))
                }
                ERROR -> {
                    assertThat(contentViewModel.feedViewState.getOrAwaitValue().contentToPlay.getOrAwaitValue().peekEvent()).isEqualTo(
                            ContentToPlay(...))
                    assertThat(contentViewModel.viewEffect.getOrAwaitValue().notifyItemChanged.getOrAwaitValue().peekEvent()).isEqualTo(
                            NotifyItemChangedEffect(...))
                }
            }
        }
    }

Answer 1

在所有（LCE）加载，内容，错误条件中保存LiveData

在ViewModel的所有LCE条件下保存ContentToPlay LiveData值或null，以确保为本地单元测试同步返回值。

Note-此策略的缺点是，它会在生产代码中不必要地向视图发出ContentToPlay值，这不是理想的，但似乎不是主要问题。

ContentViewModel.kt

    _feedViewState.value = _feedViewState.value?.copy(contentToPlay =
    switchMap(getAudiocast(contentSelected)) { lce ->
        liveData {
            when (lce) {
                is Loading -> {
                    setContentLoadingStatus(contentSelected.content.id, View.VISIBLE)
                    _viewEffect.value = _viewEffect.value?.copy(
                            notifyItemChanged = liveData {
                                emit(Event(NotifyItemChangedEffect(contentSelected.position)))
                            })
                    // Empty ContentToPlay saved.
                    emit(Event(null))
                }
                is Lce.Content -> {
                    setContentLoadingStatus(contentSelected.content.id, View.GONE)
                    _viewEffect.value = _viewEffect.value?.copy(
                            notifyItemChanged = liveData {
                                emit(Event(NotifyItemChangedEffect(contentSelected.position)))
                            })
                    // ContentToPlay saved.
                    emit(Event(lce.packet))
                }
                is Error -> {
                    setContentLoadingStatus(contentSelected.content.id, View.GONE)
                    _viewEffect.value = _viewEffect.value?.copy(
                            notifyItemChanged = liveData {
                                emit(Event(NotifyItemChangedEffect(contentSelected.position)))
                            })
                    if (lce.packet.filePath.equals(TTS_CHAR_LIMIT_ERROR))
                        _viewEffect.value = _viewEffect.value?.copy(
                                snackBar = liveData {
                                    emit(Event(SnackBarEffect(TTS_CHAR_LIMIT_ERROR_MESSAGE)))
                                })
                    else _viewEffect.value = _viewEffect.value?.copy(
                            snackBar = liveData {
                                emit(Event(SnackBarEffect(CONTENT_PLAY_ERROR)))
                            })
                    // Empty ContentToPlay saved.
                    emit(Event(null))
                }
            }
        }
    })