如何在Kotlin中用ViewModel测试协程？

implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.0"
testImplementation "androidx.arch.core:core-testing:2.1.0"
testImplementation "org.jetbrains.kotlinx:kotlinx-coroutines-test:1.5.0"

class MyViewModel : ViewModel() {
    private val data = MutableLiveData<String>()

    fun getData(): LiveData<String> {
        return data
    }

    suspend fun fetchData() {
        // 模拟网络请求延迟
        delay(1000)
        data.value = "Data from network"
    }
}

import androidx.arch.core.executor.testing.InstantTaskExecutorRule
import androidx.lifecycle.Observer
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.test.runBlockingTest
import org.junit.Assert.assertEquals
import org.junit.Before
import org.junit.Rule
import org.junit.Test
import org.mockito.Mock
import org.mockito.Mockito.verify
import org.mockito.MockitoAnnotations

@ExperimentalCoroutinesApi
class MyViewModelTest {
    @get:Rule
    val instantTaskExecutorRule = InstantTaskExecutorRule()

    private lateinit var viewModel: MyViewModel

    @Mock
    private lateinit var observer: Observer<String>

    @Before
    fun setup() {
        MockitoAnnotations.initMocks(this)
        viewModel = MyViewModel()
        viewModel.getData().observeForever(observer)
    }

    @Test
    fun `test fetchData`() = runBlockingTest {
        viewModel.fetchData()
        verify(observer).onChanged("Data from network")
        assertEquals("Data from network", viewModel.getData().value)
    }
}