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/*
* Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
*/
package kotlinx.coroutines.test
import kotlinx.coroutines.*
import kotlinx.coroutines.internal.*
import kotlin.coroutines.*
/**
* A coroutine scope that for launching test coroutines.
*
* The scope provides the following functionality:
* * The [coroutineContext] includes a [coroutine dispatcher][TestDispatcher] that supports delay-skipping, using
* a [TestCoroutineScheduler] for orchestrating the virtual time.
* This scheduler is also available via the [testScheduler] property, and some helper extension
* methods are defined to more conveniently interact with it: see [TestScope.currentTime], [TestScope.runCurrent],
* [TestScope.advanceTimeBy], and [TestScope.advanceUntilIdle].
* * When inside [runTest], uncaught exceptions from the child coroutines of this scope will be reported at the end of
* the test.
* It is invalid for child coroutines to throw uncaught exceptions when outside the call to [TestScope.runTest]:
* the only guarantee in this case is the best effort to deliver the exception.
*
* The usual way to access a [TestScope] is to call [runTest], but it can also be constructed manually, in order to
* use it to initialize the components that participate in the test.
*
* #### Differences from the deprecated [TestCoroutineScope]
*
* * This doesn't provide an equivalent of [TestCoroutineScope.cleanupTestCoroutines], and so can't be used as a
* standalone mechanism for writing tests: it does require that [runTest] is eventually called.
* The reason for this is that a proper cleanup procedure that supports using non-test dispatchers and arbitrary
* coroutine suspensions would be equivalent to [runTest], but would also be more error-prone, due to the potential
* for forgetting to perform the cleanup.
* * [TestCoroutineScope.advanceTimeBy] also calls [TestCoroutineScheduler.runCurrent] after advancing the virtual time.
* * No support for dispatcher pausing, like [DelayController] allows. [TestCoroutineDispatcher], which supported
* pausing, is deprecated; now, instead of pausing a dispatcher, one can use [withContext] to run a dispatcher that's
* paused by default, like [StandardTestDispatcher].
* * No access to the list of unhandled exceptions.
*/
@ExperimentalCoroutinesApi
public sealed interface TestScope : CoroutineScope {
/**
* The delay-skipping scheduler used by the test dispatchers running the code in this scope.
*/
@ExperimentalCoroutinesApi
public val testScheduler: TestCoroutineScheduler
}
/**
* The current virtual time on [testScheduler][TestScope.testScheduler].
* @see TestCoroutineScheduler.currentTime
*/
@ExperimentalCoroutinesApi
public val TestScope.currentTime: Long
get() = testScheduler.currentTime
/**
* Advances the [testScheduler][TestScope.testScheduler] to the point where there are no tasks remaining.
* @see TestCoroutineScheduler.advanceUntilIdle
*/
@ExperimentalCoroutinesApi
public fun TestScope.advanceUntilIdle(): Unit = testScheduler.advanceUntilIdle()
/**
* Run any tasks that are pending at the current virtual time, according to
* the [testScheduler][TestScope.testScheduler].
*
* @see TestCoroutineScheduler.runCurrent
*/
@ExperimentalCoroutinesApi
public fun TestScope.runCurrent(): Unit = testScheduler.runCurrent()
/**
* Moves the virtual clock of this dispatcher forward by [the specified amount][delayTimeMillis], running the
* scheduled tasks in the meantime.
*
* In contrast with `TestCoroutineScope.advanceTimeBy`, this function does not run the tasks scheduled at the moment
* [currentTime] + [delayTimeMillis].
*
* @throws IllegalStateException if passed a negative [delay][delayTimeMillis].
* @see TestCoroutineScheduler.advanceTimeBy
*/
@ExperimentalCoroutinesApi
public fun TestScope.advanceTimeBy(delayTimeMillis: Long): Unit = testScheduler.advanceTimeBy(delayTimeMillis)
/**
* Creates a [TestScope].
*
* It ensures that all the test module machinery is properly initialized.
* * If [context] doesn't provide a [TestCoroutineScheduler] for orchestrating the virtual time used for delay-skipping,
* a new one is created, unless either
* - a [TestDispatcher] is provided, in which case [TestDispatcher.scheduler] is used;
* - at the moment of the creation of the scope, [Dispatchers.Main] is delegated to a [TestDispatcher], in which case
* its [TestCoroutineScheduler] is used.
* * If [context] doesn't have a [TestDispatcher], a [StandardTestDispatcher] is created.
* * A [CoroutineExceptionHandler] is created that makes [TestCoroutineScope.cleanupTestCoroutines] throw if there were
* any uncaught exceptions, or forwards the exceptions further in a platform-specific manner if the cleanup was
* already performed when an exception happened. Passing a [CoroutineExceptionHandler] is illegal, unless it's an
* [UncaughtExceptionCaptor], in which case the behavior is preserved for the time being for backward compatibility.
* If you need to have a specific [CoroutineExceptionHandler], please pass it to [launch] on an already-created
* [TestCoroutineScope] and share your use case at
* [our issue tracker](https://github.com/Kotlin/kotlinx.coroutines/issues).
* * If [context] provides a [Job], that job is used as a parent for the new scope.
*
* @throws IllegalArgumentException if [context] has both [TestCoroutineScheduler] and a [TestDispatcher] linked to a
* different scheduler.
* @throws IllegalArgumentException if [context] has a [ContinuationInterceptor] that is not a [TestDispatcher].
* @throws IllegalArgumentException if [context] has an [CoroutineExceptionHandler] that is not an
* [UncaughtExceptionCaptor].
*/
@ExperimentalCoroutinesApi
@Suppress("FunctionName")
public fun TestScope(context: CoroutineContext = EmptyCoroutineContext): TestScope {
val ctxWithDispatcher = context.withDelaySkipping()
var scope: TestScopeImpl? = null
val exceptionHandler = when (ctxWithDispatcher[CoroutineExceptionHandler]) {
null -> CoroutineExceptionHandler { _, exception ->
scope!!.reportException(exception)
}
else -> throw IllegalArgumentException(
"A CoroutineExceptionHandler was passed to TestScope. " +
"Please pass it as an argument to a `launch` or `async` block on an already-created scope " +
"if uncaught exceptions require special treatment."
)
}
return TestScopeImpl(ctxWithDispatcher + exceptionHandler).also { scope = it }
}
/**
* Adds a [TestDispatcher] and a [TestCoroutineScheduler] to the context if there aren't any already.
*
* @throws IllegalArgumentException if both a [TestCoroutineScheduler] and a [TestDispatcher] are passed.
* @throws IllegalArgumentException if a [ContinuationInterceptor] is passed that is not a [TestDispatcher].
*/
internal fun CoroutineContext.withDelaySkipping(): CoroutineContext {
val dispatcher: TestDispatcher = when (val dispatcher = get(ContinuationInterceptor)) {
is TestDispatcher -> {
val ctxScheduler = get(TestCoroutineScheduler)
if (ctxScheduler != null) {
require(dispatcher.scheduler === ctxScheduler) {
"Both a TestCoroutineScheduler $ctxScheduler and TestDispatcher $dispatcher linked to " +
"another scheduler were passed."
}
}
dispatcher
}
null -> StandardTestDispatcher(get(TestCoroutineScheduler))
else -> throw IllegalArgumentException("Dispatcher must implement TestDispatcher: $dispatcher")
}
return this + dispatcher + dispatcher.scheduler
}
internal class TestScopeImpl(context: CoroutineContext) :
AbstractCoroutine(context, initParentJob = true, active = true), TestScope {
override val testScheduler get() = context[TestCoroutineScheduler]!!
private var entered = false
private var finished = false
private val uncaughtExceptions = mutableListOf()
private val lock = SynchronizedObject()
/** Called upon entry to [runTest]. Will throw if called more than once. */
fun enter() {
val exceptions = synchronized(lock) {
if (entered)
throw IllegalStateException("Only a single call to `runTest` can be performed during one test.")
entered = true
check(!finished)
uncaughtExceptions
}
if (exceptions.isNotEmpty()) {
throw UncaughtExceptionsBeforeTest().apply {
for (e in exceptions)
addSuppressed(e)
}
}
}
/** Called at the end of the test. May only be called once. */
fun leave(): List {
val exceptions = synchronized(lock) {
if(!entered || finished)
throw IllegalStateException("An internal error. Please report to the Kotlinx Coroutines issue tracker")
finished = true
uncaughtExceptions
}
val activeJobs = children.filter { it.isActive }.toList() // only non-empty if used with `runBlockingTest`
if (exceptions.isEmpty()) {
if (activeJobs.isNotEmpty())
throw UncompletedCoroutinesError(
"Active jobs found during the tear-down. " +
"Ensure that all coroutines are completed or cancelled by your test. " +
"The active jobs: $activeJobs"
)
if (!testScheduler.isIdle())
throw UncompletedCoroutinesError(
"Unfinished coroutines found during the tear-down. " +
"Ensure that all coroutines are completed or cancelled by your test."
)
}
return exceptions
}
/** Stores an exception to report after [runTest], or rethrows it if not inside [runTest]. */
fun reportException(throwable: Throwable) {
synchronized(lock) {
if (finished) {
throw throwable
} else {
uncaughtExceptions.add(throwable)
if (!entered)
throw UncaughtExceptionsBeforeTest().apply { addSuppressed(throwable) }
}
}
}
/** Throws an exception if the coroutine is not completing. */
fun tryGetCompletionCause(): Throwable? = completionCause
override fun toString(): String =
"TestScope[" + (if (finished) "test ended" else if (entered) "test started" else "test not started") + "]"
}
/** Use the knowledge that any [TestScope] that we receive is necessarily a [TestScopeImpl]. */
internal fun TestScope.asSpecificImplementation(): TestScopeImpl = when (this) {
is TestScopeImpl -> this
}
internal class UncaughtExceptionsBeforeTest : IllegalStateException(
"There were uncaught exceptions in coroutines launched from TestScope before the test started. Please avoid this," +
" as such exceptions are also reported in a platform-dependent manner so that they are not lost."
)
/**
* Thrown when a test has completed and there are tasks that are not completed or cancelled.
*/
@ExperimentalCoroutinesApi
internal class UncompletedCoroutinesError(message: String) : AssertionError(message)
