pekko/akka-actor/src/main/scala/akka/util/TestKit.scala

package akka.util

import akka.actor.{Actor, FSM}
import Actor._
import duration._

import java.util.concurrent.{BlockingDeque, LinkedBlockingDeque}

import scala.annotation.tailrec

object TestActor {
    type Ignore = Option[PartialFunction[AnyRef, Boolean]]

    case class SetTimeout(d : Duration)
    case class SetIgnore(i : Ignore)
}

class TestActor(queue : BlockingDeque[AnyRef]) extends Actor with FSM[Int, TestActor.Ignore] {
    import FSM._
    import TestActor._

    startWith(0, None)
    when(0, stateTimeout = 5 seconds) {
        case Event(SetTimeout(d), _) =>
            setStateTimeout(0, if (d.finite_?) d else None)
            stay
        case Event(SetIgnore(ign), _) => stay using ign
        case Event(StateTimeout, _) =>
            stop
        case Event(x : AnyRef, ign) =>
            val ignore = ign map (z => if (z isDefinedAt x) z(x) else false) getOrElse false
            if (!ignore) {
                queue.offerLast(x)
            }
            stay
    }
    initialize
}

/**
 * Test kit for testing actors. Inheriting from this trait enables reception of
 * replies from actors, which are queued by an internal actor and can be
 * examined using the `expectMsg...` methods. Assertions and bounds concerning
 * timing are available in the form of `within` blocks.
 *
 * <pre>
 * class Test extends TestKit {
 *     val test = actorOf[SomeActor].start
 *
 *     within (1 second) {
 *         test ! SomeWork
 *         expectMsg(Result1) // bounded to 1 second
 *         expectMsg(Result2) // bounded to the remainder of the 1 second
 *     }
 * }
 * </pre>
 *
 * Beware of two points:
 *
 *  - the internal test actor needs to be stopped, either explicitly using
 *    `stopTestActor` or implicitly by using its internal inactivity timeout,
 *    see `setTestActorTimeout`
 *  - this trait is not thread-safe (only one actor with one queue, one stack
 *    of `within` blocks); it is expected that the code is executed from a
 *    constructor as shown above, which makes this a non-issue, otherwise take
 *    care not to run tests within a single test class instance in parallel.
 *
 * @author Roland Kuhn
 * @since 1.1
 */
trait TestKit {

    private val queue = new LinkedBlockingDeque[AnyRef]()
    
    /**
     * ActorRef of the test actor. Access is provided to enable e.g.
     * registration as message target.
     */
    protected val testActor = actorOf(new TestActor(queue)).start

    /**
     * Implicit sender reference so that replies are possible for messages sent
     * from the test class.
     */
    protected implicit val senderOption = Some(testActor)

    private var end : Duration = Duration.Inf
    /*
     * THIS IS A HACK: expectNoMsg and receiveWhile are bounded by `end`, but
     * running them should not trigger an AssertionError, so mark their end
     * time here and do not fail at the end of `within` if that time is not
     * long gone.
     */
    private var lastSoftTimeout : Duration = now - 5.millis

    /**
     * Stop test actor. Should be done at the end of the test unless relying on
     * test actor timeout.
     */
    def stopTestActor { testActor.stop }

    /**
     * Set test actor timeout. By default, the test actor shuts itself down
     * after 5 seconds of inactivity. Set this to Duration.Inf to disable this
     * behavior, but make sure that someone will then call `stopTestActor`,
     * unless you want to leak actors, e.g. wrap test in
     *
     * <pre>
     *   try {
     *     ...
     *   } finally { stopTestActor }
     * </pre>
     */
    def setTestActorTimeout(d : Duration) { testActor ! TestActor.SetTimeout(d) }

    /**
     * Ignore all messages in the test actor for which the given partial
     * function returns true.
     */
    def ignoreMsg(f : PartialFunction[AnyRef, Boolean]) { testActor ! TestActor.SetIgnore(Some(f)) }

    /**
     * Stop ignoring messages in the test actor.
     */
    def ignoreNoMsg { testActor ! TestActor.SetIgnore(None) }

    /**
     * Obtain current time (`System.currentTimeMillis`) as Duration.
     */
    def now : Duration = System.nanoTime.nanos

    /**
     * Obtain time remaining for execution of the innermost enclosing `within` block.
     */
    def remaining : Duration = end - now

    /**
     * Execute code block while bounding its execution time between `min` and
     * `max`. `within` blocks may be nested. All methods in this trait which
     * take maximum wait times are available in a version which implicitly uses
     * the remaining time governed by the innermost enclosing `within` block.
     *
     * <pre>
     * val ret = within(50 millis) {
     *             test ! "ping"
     *             expectMsgClass(classOf[String])
     *           }
     * </pre>
     */
    def within[T](min : Duration, max : Duration)(f : => T) : T = {
        val start = now
        val rem = end - start
        assert (rem >= min, "required min time "+min+" not possible, only "+rem+" left")

        val max_diff = if (max < rem) max else rem
        val prev_end = end
        end = start + max_diff

        val ret = f

        val diff = now - start
        assert (min <= diff, "block took "+diff+", should at least have been "+min)
        /*
         * caution: HACK AHEAD
         */
        if (now - lastSoftTimeout > 5.millis) {
            assert (diff <= max_diff, "block took "+diff+", exceeding "+max_diff)
        } else {
            lastSoftTimeout -= 5.millis
        }

        end = prev_end
        ret
    }

    /**
     * Same as calling `within(0 seconds, max)(f)`.
     */
    def within[T](max : Duration)(f : => T) : T = within(0 seconds, max)(f)

    /**
     * Same as `expectMsg`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsg(obj : Any) : AnyRef = expectMsg(remaining, obj)

    /**
     * Receive one message from the test actor and assert that it equals the
     * given object. Wait time is bounded by the given duration, with an
     * AssertionFailure being thrown in case of timeout.
     *
     * @return the received object
     */
    def expectMsg(max : Duration, obj : Any) : AnyRef = {
        val o = receiveOne(max)
        assert (o ne null, "timeout during expectMsg")
        assert (obj == o, "expected "+obj+", found "+o)
        o
    }

    /**
     * Same as `expectMsg`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsg[T](f : PartialFunction[Any, T]) : T = expectMsg(remaining)(f)

    /**
     * Receive one message from the test actor and assert that the given
     * partial function accepts it. Wait time is bounded by the given duration,
     * with an AssertionFailure being thrown in case of timeout.
     *
     * Use this variant to implement more complicated or conditional
     * processing.
     *
     * @return the received object as transformed by the partial function
     */
    def expectMsg[T](max : Duration)(f : PartialFunction[Any, T]) : T = {
        val o = receiveOne(max)
        assert (o ne null, "timeout during expectMsg")
        assert (f.isDefinedAt(o), "does not match: "+o)
        f(o)
    }

    /**
     * Same as `expectMsgClass`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgClass[C](c : Class[C]) : C = expectMsgClass(remaining, c)

    /**
     * Receive one message from the test actor and assert that it conforms to
     * the given class. Wait time is bounded by the given duration, with an
     * AssertionFailure being thrown in case of timeout.
     *
     * @return the received object
     */
    def expectMsgClass[C](max : Duration, c : Class[C]) : C = {
        val o = receiveOne(max)
        assert (o ne null, "timeout during expectMsgClass")
        assert (c isInstance o, "expected "+c+", found "+o.getClass)
        o.asInstanceOf[C]
    }

    /**
     * Same as `expectMsgAnyOf`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgAnyOf(obj : Any*) : AnyRef = expectMsgAnyOf(remaining, obj : _*)

    /**
     * Receive one message from the test actor and assert that it equals one of
     * the given objects. Wait time is bounded by the given duration, with an
     * AssertionFailure being thrown in case of timeout.
     *
     * @return the received object
     */
    def expectMsgAnyOf(max : Duration, obj : Any*) : AnyRef = {
        val o = receiveOne(max)
        assert (o ne null, "timeout during expectMsgAnyOf")
        assert (obj exists (_ == o), "found unexpected "+o)
        o
    }

    /**
     * Same as `expectMsgAnyClassOf`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgAnyClassOf(obj : Class[_]*) : AnyRef = expectMsgAnyClassOf(remaining, obj : _*)

    /**
     * Receive one message from the test actor and assert that it conforms to
     * one of the given classes. Wait time is bounded by the given duration,
     * with an AssertionFailure being thrown in case of timeout.
     *
     * @return the received object
     */
    def expectMsgAnyClassOf(max : Duration, obj : Class[_]*) : AnyRef = {
        val o = receiveOne(max)
        assert (o ne null, "timeout during expectMsgAnyClassOf")
        assert (obj exists (_ isInstance o), "found unexpected "+o)
        o
    }

    /**
     * Same as `expectMsgAllOf`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgAllOf(obj : Any*) { expectMsgAllOf(remaining, obj : _*) }

    /**
     * Receive a number of messages from the test actor matching the given
     * number of objects and assert that for each given object one is received
     * which equals it. This construct is useful when the order in which the
     * objects are received is not fixed. Wait time is bounded by the given
     * duration, with an AssertionFailure being thrown in case of timeout.
     *
     * <pre>
     * within(1 second) {
     *   dispatcher ! SomeWork1()
     *   dispatcher ! SomeWork2()
     *   expectMsgAllOf(Result1(), Result2())
     * }
     * </pre>
     */
    def expectMsgAllOf(max : Duration, obj : Any*) {
        val recv = receiveN(obj.size, now + max)
        assert (obj forall (x => recv exists (x == _)), "not found all")
    }

    /**
     * Same as `expectMsgAllClassOf`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgAllClassOf(obj : Class[_]*) { expectMsgAllClassOf(remaining, obj : _*) }

    /**
     * Receive a number of messages from the test actor matching the given
     * number of classes and assert that for each given class one is received
     * which is of that class (equality, not conformance). This construct is
     * useful when the order in which the objects are received is not fixed.
     * Wait time is bounded by the given duration, with an AssertionFailure
     * being thrown in case of timeout.
     */
    def expectMsgAllClassOf(max : Duration, obj : Class[_]*) {
        val recv = receiveN(obj.size, now + max)
        assert (obj forall (x => recv exists (_.getClass eq x)), "not found all")
    }

    /**
     * Same as `expectMsgAllConformingOf`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectMsgAllConformingOf(obj : Class[_]*) { expectMsgAllClassOf(remaining, obj : _*) }

    /**
     * Receive a number of messages from the test actor matching the given
     * number of classes and assert that for each given class one is received
     * which conforms to that class. This construct is useful when the order in
     * which the objects are received is not fixed.  Wait time is bounded by
     * the given duration, with an AssertionFailure being thrown in case of
     * timeout.
     *
     * Beware that one object may satisfy all given class constraints, which
     * may be counter-intuitive.
     */
    def expectMsgAllConformingOf(max : Duration, obj : Class[_]*) {
        val recv = receiveN(obj.size, now + max)
        assert (obj forall (x => recv exists (x isInstance _)), "not found all")
    }

    /**
     * Same as `expectNoMsg`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def expectNoMsg { expectNoMsg(remaining) }

    /**
     * Assert that no message is received for the specified time.
     */
    def expectNoMsg(max : Duration) {
        val o = receiveOne(max)
        assert (o eq null, "received unexpected message "+o)
        lastSoftTimeout = now
    }

    /**
     * Same as `receiveWhile`, but takes the maximum wait time from the innermost
     * enclosing `within` block.
     */
    def receiveWhile[T](f : PartialFunction[AnyRef, T]) : Seq[T] = receiveWhile(remaining)(f)

    /**
     * Receive a series of messages as long as the given partial function
     * accepts them or the idle timeout is met or the overall maximum duration
     * is elapsed. Returns the sequence of messages.
     *
     * Beware that the maximum duration is not implicitly bounded by or taken
     * from the innermost enclosing `within` block, as it is not an error to
     * hit the `max` duration in this case.
     *
     * One possible use of this method is for testing whether messages of
     * certain characteristics are generated at a certain rate:
     *
     * <pre>
     * test ! ScheduleTicks(100 millis)
     * val series = receiveWhile(750 millis) {
     *     case Tick(count) => count
     * }
     * assert(series == (1 to 7).toList)
     * </pre>
     */
    def receiveWhile[T](max : Duration)(f : PartialFunction[AnyRef, T]) : Seq[T] = {
        val stop = now + max

        @tailrec def doit(acc : List[T]) : List[T] = {
            receiveOne(stop - now) match {
                case null =>
                    acc.reverse
                case o if (f isDefinedAt o) =>
                    doit(f(o) :: acc)
                case o =>
                    queue.offerFirst(o)
                    acc.reverse
            }
        }

        val ret = doit(Nil)
        lastSoftTimeout = now
        ret
    }

    private def receiveN(n : Int, stop : Duration) : Seq[AnyRef] = {
        for { x <- 1 to n } yield {
            val timeout = stop - now
            val o = receiveOne(timeout)
            assert (o ne null, "timeout while expecting "+n+" messages")
            o
        }
    }

    private def receiveOne(max : Duration) : AnyRef = {
        if (max == 0.seconds) {
            queue.pollFirst
        } else if (max.finite_?) {
            queue.pollFirst(max.length, max.unit)
        } else {
            queue.takeFirst
        }
    }
}

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