Update TestCoroutineContext to support structured concurrency.

Author: objcode

core/kotlinx-coroutines-core/src/test_/TestBuilders.kt

@@ -0,0 +1,190 @@
+package kotlinx.coroutines.test
+
+import kotlinx.coroutines.*
+import java.util.concurrent.TimeoutException
+import kotlin.coroutines.ContinuationInterceptor
+import kotlin.coroutines.CoroutineContext
+
+/**
+ * Executes a [testBody] in a [TestCoroutineScope] which provides detailed control over the execution of coroutines.
+ *
+ * This function should be used when you need detailed control over the execution of your test. For most tests consider
+ * using [runBlockingTest].
+ *
+ * Code executed in a `asyncTest` will dispatch lazily. That means calling builders such as [launch] or [async] will
+ * not execute the block immediately. You can use methods like [TestCoroutineScope.runCurrent] and
+ * [TestCoroutineScope.advanceTimeTo] on the [TestCoroutineScope]. For a full list of execution methods see
+ * [DelayController].
+ *
+ * ```
+ * @Test
+ * fun exampleTest() = asyncTest {
+ *     // 1: launch will execute but not run the body
+ *     launch  {
+ *         // 3: the body of launch will execute in response to runCurrent [currentTime = 0ms]
+ *         delay(1_000)
+ *         // 5: After the time is advanced, delay(1_000) will return [currentTime = 1000ms]
+ *         println("Faster delays!")
+ *     }
+ *
+ *     // 2: use runCurrent() to execute the body of launch [currentTime = 0ms]
+ *     runCurrent()
+ *
+ *     // 4: advance the dispatcher "time" by 1_000, which will resume after the delay
+ *     advanceTimeTo(1_000)
+ *
+ * ```
+ *
+ * This method requires that all coroutines launched inside [testBody] complete, or are cancelled, as part of the test
+ * conditions.
+ *
+ * In addition any unhandled exceptions thrown in coroutines must be rethrown by
+ * [TestCoroutineScope.rethrowUncaughtCoroutineException] or cleared via [TestCoroutineScope.exceptions] inside of
+ * [testBody].
+ *
+ * @throws UncompletedCoroutinesError If the [testBody] does not complete (or cancel) all coroutines that it launches
+ * (including coroutines suspended on await).
+ * @throws UnhandledExceptionsError If an uncaught exception is not handled by [testBody]
+ *
+ * @param dispatcher An optional dispatcher, during [testBody] execution [TestCoroutineDispatcher.dispatchImmediately] will be set to false
+ * @param testBody The code of the unit-test.
+ *
+ * @see [runBlockingTest]
+ */
+fun asyncTest(context: CoroutineContext? = null, testBody: TestCoroutineScope.() -> Unit) {
+    val (safeContext, dispatcher) = context.checkArguments()
+    // smart cast dispatcher to expose interface
+    dispatcher as DelayController
+    val scope = TestCoroutineScope(safeContext)
+
+    val oldDispatch = dispatcher.dispatchImmediately
+    dispatcher.dispatchImmediately = false
+
+    try {
+        scope.testBody()
+        scope.cleanupTestCoroutines()
+
+        // check for any active child jobs after cleanup (e.g. coroutines suspended on calls to await)
+        val job = checkNotNull(safeContext[Job]) { "Job required for asyncTest" }
+        val activeChildren = job.children.filter { it.isActive }.toList()
+        if (activeChildren.isNotEmpty()) {
+            throw UncompletedCoroutinesError("Test finished with active jobs: ${activeChildren}")
+        }
+    } finally {
+        dispatcher.dispatchImmediately = oldDispatch
+    }
+}
+
+/**
+ * @see [asyncTest]
+ */
+fun TestCoroutineScope.asyncTest(testBody: TestCoroutineScope.() -> Unit) =
+        asyncTest(coroutineContext, testBody)
+
+
+/**
+ * Executes a [testBody] inside an immediate execution dispatcher.
+ *
+ * This is similar to [runBlocking] but it will immediately progress past delays and into [launch] and [async] blocks.
+ * You can use this to write tests that execute in the presence of calls to [delay] without causing your test to take
+ * extra time.
+ *
+ * Compared to [asyncTest], it provides a smaller API for tests that don't need detailed control over execution.
+ *
+ * ```
+ * @Test
+ * fun exampleTest() = runBlockingTest {
+ *     val deferred = async {
+ *         delay(1_000)
+ *         async {
+ *             delay(1_000)
+ *         }.await()
+ *     }
+ *
+ *     deferred.await() // result available immediately
+ * }
+ *
+ * ```
+ *
+ * [runBlockingTest] will allow tests to finish successfully while started coroutines are unfinished. In addition unhandled
+ * exceptions inside coroutines will not fail the test.
+ *
+ * @param dispatcher An optional dispatcher, during [testBody] execution [TestCoroutineDispatcher.dispatchImmediately] will be set to true
+ * @param testBody The code of the unit-test.
+ *
+ * @see [asyncTest]
+ */
+fun runBlockingTest(context: CoroutineContext? = null, testBody: suspend CoroutineScope.() -> Unit) {
+    val (safeContext, dispatcher) = context.checkArguments()
+    // smart cast dispatcher to expose interface
+    dispatcher as DelayController
+
+    val oldDispatch = dispatcher.dispatchImmediately
+    dispatcher.dispatchImmediately = true
+    val scope = TestCoroutineScope(safeContext)
+    try {
+        runBlocking(scope.coroutineContext) {
+            scope.testBody()
+            scope.cleanupTestCoroutines()
+        }
+    } finally {
+        dispatcher.dispatchImmediately = oldDispatch
+    }
+}
+
+/**
+ * Convenience method for calling runBlocking on an existing [TestCoroutineScope].
+ *
+ * [block] will be executed in immediate execution mode, similar to [runBlockingTest].
+ */
+fun <T> TestCoroutineScope.runBlocking(block: suspend CoroutineScope.() -> T): T {
+    val oldDispatch = dispatchImmediately
+    dispatchImmediately = true
+    try {
+        return runBlocking(coroutineContext, block)
+    } finally {
+        dispatchImmediately = oldDispatch
+    }
+}
+
+/**
+ * Convenience method for calling runBlocking on an existing [TestCoroutineDispatcher].
+ *
+ * [block] will be executed in immediate execution mode, similar to [runBlockingTest].
+ */
+fun <T> TestCoroutineDispatcher.runBlocking(block: suspend CoroutineScope.() -> T): T {
+    val oldDispatch = dispatchImmediately
+    dispatchImmediately = true
+    try {
+        return runBlocking(this, block)
+    } finally {
+        dispatchImmediately = oldDispatch
+    }
+}
+
+private fun CoroutineContext?.checkArguments(): Pair<CoroutineContext, ContinuationInterceptor> {
+    var safeContext= this ?: TestCoroutineExceptionHandler() + TestCoroutineDispatcher()
+
+    val dispatcher = safeContext[ContinuationInterceptor].run {
+        this?.let {
+            if (this !is DelayController) {
+                throw IllegalArgumentException("Dispatcher must implement DelayController")
+            }
+        }
+        this ?: TestCoroutineDispatcher()
+    }
+
+    val exceptionHandler = safeContext[CoroutineExceptionHandler].run {
+        this?.let {
+            if (this !is ExceptionCaptor) {
+                throw IllegalArgumentException("coroutineExceptionHandler must implement ExceptionCaptor")
+            }
+        }
+        this ?: TestCoroutineExceptionHandler()
+    }
+
+    val job = safeContext[Job] ?: SupervisorJob()
+
+    safeContext = safeContext + dispatcher + exceptionHandler + job
+    return Pair(safeContext, dispatcher)
+}