unit-testing - Kotlin 协程单元测试失败，错误为 "Module with the Main dispatcher had failed to initialize"

Question

对使用 withContext(Dispatchers.Main) 的 kotlin 挂起方法运行单元测试时测试方法失败，但有以下异常:

我的协程库版本是 kotlinx-coroutines-core:1.1.1 和 kotlinx-coroutines-android:1.1.1

示例:

suspend fun methodToTest() {
        withContext(Dispatchers.Main) {
           doSomethingOnMainThread()
                val data = withContext(Dispatchers.IO) {
                    doSomethingOnIOThread()
                }
        }
    }

另外，当我删除 withContext(Dispatchers.Main) 时它工作正常。

java.lang.IllegalStateException: Module with the Main dispatcher had failed to initialize. For tests Dispatchers.setMain from kotlinx-coroutines-test module can be used

at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.missing(MainDispatchers.kt:79)
at kotlinx.coroutines.internal.MissingMainCoroutineDispatcher.isDispatchNeeded(MainDispatchers.kt:54)
at kotlinx.coroutines.DispatchedKt.resumeCancellable(Dispatched.kt:373)
at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:25)
at kotlinx.coroutines.BuildersKt__Builders_commonKt.withContext(Builders.common.kt:152)
at kotlinx.coroutines.BuildersKt.withContext(Unknown Source)

Answer 1

您无权在单元测试中访问 Dispatchers.Main

见 https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-test/
Dispatchers.Main Delegation部分详细说明了您需要做什么。