junit Android单元测试Kotlin:从未设置LiveData值

ntjbwcob  于 2022-11-11  发布在  Android
关注(0)|答案(1)|浏览(169)

单元测试时出现此错误:“从未设置LiveData值。”
我尝试测试视图模型的getStudents()方法,如下所示:
学生视图模型:

@HiltViewModel
class StudentViewModel @Inject constructor(
    private val getStudentsUseCase: GetStudentsUseCase
) : ViewModel() {
    private val _studentLD = MutableLiveData<List<Student>>()
    val studentLD: LiveData<List<Student>> = _studentLD

    private val _errorLD = MutableLiveData<String>()
    val errorLD: LiveData<String> = _errorLD

    fun getStudents() {
        viewModelScope.launch {
            var result = getStudentsUseCase.execute()
            result.onSuccess {
                _studentLD.value = it
            }.onFailure {
                _errorLD.value = it.message.toString()
            }
        }
    }
}

学生视图模型测试:

@OptIn(ExperimentalCoroutinesApi::class)
class StudentViewModelTest {

    private lateinit var viewModel: StudentViewModel

    @get:Rule
    var instantExecutorRule = InstantTaskExecutorRule()

    @get:Rule
    var mainCoroutineRule = MainCoroutineRule()

    @Mock
    private lateinit var getStudentsUseCase: GetStudentsUseCase

    private var studentList = listOf(
        Student("Max", "122d"),
        Student("Steven", "012s")
    )

    @Before
    fun setUp() {
        MockitoAnnotations.initMocks(this)
        viewModel = StudentViewModel(getStudentsUseCase)
    }

    @Test
    fun getStudentsSuccess() = runTest {
        Mockito.`when`(getStudentsUseCase.execute()).thenReturn(Result.success(studentList))

        viewModel.getStudents()
        val value = viewModel.studentLD.getOrAwaitValueTest()
        assertEquals(value, studentList)
    }
}

我做错了什么?我也有一个LiveDataTest类,其中定义了getOrAwaitValueTest()方法。提前感谢
编辑:此外,getOrAwaitValueTest()方法在此处定义如下:

@VisibleForTesting(otherwise = VisibleForTesting.NONE)
fun <T> LiveData<T>.getOrAwaitValueTest(
    time: Long = 2,
    timeUnit: TimeUnit = TimeUnit.SECONDS,
    afterObserve: () -> Unit = {}
): T {
    var data: T? = null
    val latch = CountDownLatch(1)
    val observer = object : Observer<T> {
        override fun onChanged(o: T?) {
            data = o
            latch.countDown()
            this@getOrAwaitValueTest.removeObserver(this)
        }
    }
    this.observeForever(observer)

    try {
        afterObserve.invoke()

        // Don't wait indefinitely if the LiveData is not set.
        if (!latch.await(time, timeUnit)) {
            throw TimeoutException("LiveData value was never set.")
        }

    } finally {
        this.removeObserver(observer)
    }

    @Suppress("UNCHECKED_CAST")
    return data as T
}
yzxexxkh

yzxexxkh1#

我找到了一个解决办法:要使其正常工作,您需要添加advanceUntilIdle()方法。
立即执行所有挂起的任务,并将虚拟时钟时间提前到最后一个延迟。如果由于虚拟时间提前而调度了新任务,则将在advanceUntilIdle返回之前执行这些任务。

@Test
fun getStudentsSuccess() = runTest {
        Mockito.`when`(getStudentsUseCase.execute()).thenReturn(Result.success(studentList))

        viewModel.getStudents()
        advanceUntilIdle()
        val value = viewModel.studentLD.getOrAwaitValueTest()

        assertEquals(value, studentList)
}

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