延迟对 Kotlin 协程进行单元测试
[英]Unit testing a Kotlin coroutine with delay
问题描述
I'm trying to unit test a Kotlin coroutine that uses delay() .
我正在尝试对使用delay()的 Kotlin 协程进行单元测试。 For the unit test I don't care about the delay() , it's just slowing the test down.对于单元测试，我不关心delay() ，它只是减慢了测试速度。 I'd like to run the test in some way that doesn't actually delay when delay() is called.我想以某种方式运行测试，当调用delay()时实际上不会延迟。
I tried running the coroutine using a custom context which delegates to CommonPool:我尝试使用委托给 CommonPool 的自定义上下文运行协程：
class TestUiContext : CoroutineDispatcher(), Delay {
suspend override fun delay(time: Long, unit: TimeUnit) {
// I'd like it to call this
}
override fun scheduleResumeAfterDelay(time: Long, unit: TimeUnit, continuation: CancellableContinuation<Unit>) {
// but instead it calls this
}
override fun dispatch(context: CoroutineContext, block: Runnable) {
CommonPool.dispatch(context, block)
}
}
I was hoping I could just return from my context's delay() method, but instead it's calling my scheduleResumeAfterDelay() method, and I don't know how to delegate that to the default scheduler.我希望我可以从我的上下文的delay()方法返回，但它正在调用我的scheduleResumeAfterDelay()方法，我不知道如何将它委托给默认的调度程序。
4 个解决方案
解决方案1
26 2018-03-02 22:24:10
If you don't want any delay, why don't you simply resume the continuation in the schedule call?:如果您不想有任何延迟，为什么不简单地在 schedule 调用中恢复延续？：
class TestUiContext : CoroutineDispatcher(), Delay {
override fun scheduleResumeAfterDelay(time: Long, unit: TimeUnit, continuation: CancellableContinuation<Unit>) {
continuation.resume(Unit)
}
override fun dispatch(context: CoroutineContext, block: Runnable) {
//CommonPool.dispatch(context, block) // dispatch on CommonPool
block.run() // dispatch on calling thread
}
}
That way delay() will resume with no delay.这样delay()将立即恢复。 Note that this still suspends at delay, so other coroutines can still run (like yield() )请注意，这仍然会延迟挂起，因此其他协程仍然可以运行（例如yield() ）
@Test
fun `test with delay`() {
runBlocking(TestUiContext()) {
launch { println("launched") }
println("start")
delay(5000)
println("stop")
}
}
Runs without delay and prints:立即运行并打印：
start
launched
stop
EDIT:编辑：
You can control where the continuation is run by customizing the dispatch function.您可以通过自定义dispatch函数来控制在何处运行延续。
解决方案2
14 已采纳 2019-09-05 16:51:53
In kotlinx.coroutines v1.2.1 they added the kotlinx-coroutines-test module.在 kotlinx.coroutines v1.2.1 中，他们添加了kotlinx-coroutines-test模块。 It includes the runBlockingTest coroutine builder, as well as a TestCoroutineScope and TestCoroutineDispatcher .它包括runBlockingTest协程构建器，以及TestCoroutineScope和TestCoroutineDispatcher 。 They allow auto-advancing time, as well as explicitly controlling time for testing coroutines with delay .它们允许自动推进时间，以及使用delay显式控制测试协程的delay 。
解决方案3
4 2018-08-01 21:56:34
In kotlinx.coroutines v0.23.0 they introduced a TestCoroutineContext .在 kotlinx.coroutines v0.23.0 中，他们引入了一个TestCoroutineContext 。
Pro: it makes truly testing coroutines with delay possible.优点：它使真正的delay测试协程成为可能。 You can set the CoroutineContext's virtual clock to a moment in time and verify the expected behavior.您可以将 CoroutineContext 的虚拟时钟设置为某个时刻并验证预期的行为。
Con: if your coroutine code doesn't use delay , and you just want it to execute synchronously on the calling thread, it is slightly more cumbersome to use than the TestUiContext from @bj0's answer (you need to call triggerActions() on the TestCoroutineContext to get the coroutine to execute).缺点：如果您的协程代码不使用delay ，而您只是希望它在调用线程上同步执行，那么使用它比 @bj0 的答案中的TestUiContext稍微麻烦一些（您需要在triggerActions()上调用triggerActions()使协程执行）。
Sidenote: The TestCoroutineContext now lives in the kotlinx-coroutines-test module starting with coroutines version 1.2.1, and will be marked deprecated or not exist in the standard coroutine library in versions above this version.旁注： TestCoroutineContext现在位于kotlinx-coroutines-test模块中，从协程版本 1.2.1 开始，在此版本以上的版本中，将在标准协程库中标记为已弃用或不存在。
解决方案4
4 2020-06-15 21:20:50
Use TestCoroutineDispatcher, TestCoroutineScope, or Delay使用 TestCoroutineDispatcher、TestCoroutineScope 或 Delay
TestCoroutineDispatcher, TestCoroutineScope, or Delay can be used to handle a delay in a Kotlin coroutine made in the production code tested. TestCoroutineDispatcher、TestCoroutineScope 或 Delay 可用于处理在测试的生产代码中产生的 Kotlin 协程中的delay 。
Implement实施
In this case SomeViewModel 's view state is being tested.在这种情况下， SomeViewModel的视图状态正在被测试。 In the ERROR state a view state is emitted with the error value being true.在ERROR状态下，会发出一个视图状态，错误值为 true。 After the defined Snackbar time length has passed using a delay a new view state is emitted with the error value set to false.在使用delay超过定义的 Snackbar 时间长度后，会发出一个新的视图状态，错误值设置为 false。
SomeViewModel.kt SomeViewModel.kt
private fun loadNetwork() {
repository.getData(...).onEach {
when (it.status) {
LOADING -> ...
SUCCESS ...
ERROR -> {
_viewState.value = FeedViewState.SomeFeedViewState(
isLoading = false,
feed = it.data,
isError = true
)
delay(SNACKBAR_LENGTH)
_viewState.value = FeedViewState.SomeFeedViewState(
isLoading = false,
feed = it.data,
isError = false
)
}
}
}.launchIn(coroutineScope)
}
There are numerous ways to handle the delay .有多种方法可以处理delay 。 advanceUntilIdle is good because it doesn't require specifying a hardcoded length. advanceUntilIdle很好，因为它不需要指定硬编码长度。 Also, if injecting the TestCoroutineDispatcher, as outlined by Craig Russell , this will be handled by the same dispatcher used inside of the ViewModel.此外，如果注入 TestCoroutineDispatcher，如Craig Russell 所述，这将由 ViewModel 内部使用的相同调度程序处理。
SomeTest.kt SomeTest.kt
private val testDispatcher = TestCoroutineDispatcher()
private val testScope = TestCoroutineScope(testDispatcher)
// Code that initiates the ViewModel emission of the view state(s) here.
testDispatcher.advanceUntilIdle()
These will also work:这些也将起作用：
-
testScope.advanceUntilIdle() -
testDispatcher.delay(SNACKBAR_LENGTH) -
delay(SNACKBAR_LENGTH) -
testDispatcher.resumeDispatcher() -
testScope.resumeDispatcher() -
testDispatcher.advanceTimeBy(SNACKBAR_LENGTH) -
testScope.advanceTimeBy(SNACKBAR_LENGTH)
Error without handling the delay没有处理延迟的错误
kotlinx.coroutines.test.UncompletedCoroutinesError: Unfinished coroutines during teardown.
at kotlinx.coroutines.test.TestCoroutineDispatcher.cleanupTestCoroutines(TestCoroutineDispatcher.kt:178) at app.topcafes.FeedTest.cleanUpTest(FeedTest.kt:127) at app.topcafes.FeedTest.access$cleanUpTest(FeedTest.kt:28) at app.topcafes.FeedTest$topCafesTest$1.invokeSuspend(FeedTest.kt:106) at app.topcafes.FeedTest$topCafesTest$1.invoke(FeedTest.kt) at kotlinx.coroutines.test.TestBuildersKt$runBlockingTest$deferred$1.invokeSuspend(TestBuilders.kt:50) at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33) at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:56) at kotlinx.coroutines.test.TestCoroutineDispatcher.dispatch(TestCoroutineDispatcher.kt:50) at kotlinx.coroutines.DispatchedContinuationKt.resumeCancellableWith(DispatchedContinuation.kt:288) at kotlinx.coroutines.intrinsics.CancellableKt.startCoroutineCancellable(Cancellable.kt:26) at kotlinx.coroutines.CoroutineStart.invoke(CoroutineStart.kt:109) at kotlinx.coroutines.AbstractCoroutine.star
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