Add actorbintree assignment

.gitignore

@@ -0,0 +1,16 @@
+# General
+*.DS_Store
+*.swp
+*~
+
+# Dotty
+*.class
+*.tasty
+*.hasTasty
+
+# sbt
+target/
+
+# Dotty IDE
+/.dotty-ide-artifact
+/.dotty-ide.json

.gitlab-ci.yml

@@ -0,0 +1,36 @@
+# DO NOT EDIT THIS FILE
+
+stages:
+  - build
+  - grade
+
+compile:
+  stage: build
+  image: lampepfl/moocs:dotty-2020-02-12
+  except:
+    - tags
+  tags:
+    - cs206
+  script:
+    - sbt packageSubmission
+  artifacts:
+    expire_in: 1 day
+    paths:
+      - submission.jar
+
+grade:
+  stage: grade
+  except:
+    - tags
+  tags:
+    - cs206
+  image:
+    name: smarter3/moocs:reactive-actorbintree-2020-04-15
+    entrypoint: [""]
+  allow_failure: true
+  before_script:
+    - mkdir -p /shared/submission/
+    - cp submission.jar /shared/submission/submission.jar
+  script:
+    - cd /grader
+    - /grader/grade | /grader/feedback-printer

.vscode/settings.json

@@ -0,0 +1,8 @@
+{
+  "dotty": {
+    "trace": {
+      "remoteTracingUrl": "wss://lamppc36.epfl.ch/dotty-remote-tracer/upload/lsp.log",
+      "server": { "format": "JSON", "verbosity": "verbose" }
+    }
+  }
+}

assignment.sbt

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+// Student tasks (i.e. submit, packageSubmission)
+enablePlugins(StudentTasks)
+
+

build.sbt

@@ -0,0 +1,24 @@
+course := "reactive"
+assignment := "actorbintree"
+
+testOptions in Test += Tests.Argument(TestFrameworks.JUnit, "-a", "-v", "-s")
+parallelExecution in Test := false
+
+val akkaVersion = "2.6.0"
+
+scalaVersion := "0.23.0-bin-20200211-5b006fb-NIGHTLY"
+
+scalacOptions ++= Seq(
+  "-feature",
+  "-deprecation",
+  "-encoding", "UTF-8",
+  "-unchecked",
+  "-language:implicitConversions"
+)
+
+libraryDependencies ++= Seq(
+  "com.typesafe.akka"        %% "akka-actor"         % akkaVersion,
+  "com.typesafe.akka"        %% "akka-testkit"       % akkaVersion % Test,
+  "com.novocode"             % "junit-interface"     % "0.11"      % Test
+).map(_.withDottyCompat(scalaVersion.value))
+testSuite := "actorbintree.BinaryTreeSuite"

project/MOOCSettings.scala

@@ -0,0 +1,46 @@
+package ch.epfl.lamp
+
+import sbt._
+import sbt.Keys._
+
+/**
+ * Coursera uses two versions of each assignment. They both have the same assignment key and part id but have
+ * different item ids.
+ *
+ * @param key Assignment key
+ * @param partId Assignment partId
+ * @param itemId Item id of the non premium version
+ * @param premiumItemId Item id of the premium version (`None` if the assignment is optional)
+ */
+case class CourseraId(key: String, partId: String, itemId: String, premiumItemId: Option[String])
+
+/**
+  * Settings shared by all assignments, reused in various tasks.
+  */
+object MOOCSettings extends AutoPlugin {
+
+  object autoImport {
+    val course = SettingKey[String]("course")
+    val assignment = SettingKey[String]("assignment")
+    val options = SettingKey[Map[String, Map[String, String]]]("options")
+    val courseraId = settingKey[CourseraId]("Coursera-specific information identifying the assignment")
+    val testSuite = settingKey[String]("Fully qualified name of the test suite of this assignment")
+    // Convenient alias
+    type CourseraId = ch.epfl.lamp.CourseraId
+    val CourseraId = ch.epfl.lamp.CourseraId
+  }
+
+  import autoImport._
+
+  override val globalSettings: Seq[Def.Setting[_]] = Seq(
+    // supershell is verbose, buggy and useless.
+    useSuperShell := false
+  )
+
+  override val projectSettings: Seq[Def.Setting[_]] = Seq(
+    parallelExecution in Test := false,
+    // Report test result after each test instead of waiting for every test to finish
+    logBuffered in Test := false,
+    name := s"${course.value}-${assignment.value}"
+  )
+}

project/StudentTasks.scala

@@ -0,0 +1,318 @@
+package ch.epfl.lamp
+
+import sbt._
+import Keys._
+
+// import scalaj.http._
+import java.io.{File, FileInputStream, IOException}
+import org.apache.commons.codec.binary.Base64
+// import play.api.libs.json.{Json, JsObject, JsPath}
+import scala.util.{Failure, Success, Try}
+
+/**
+  * Provides tasks for submitting the assignment
+  */
+object StudentTasks extends AutoPlugin {
+
+  override def requires = super.requires && MOOCSettings
+
+  object autoImport {
+    val packageSourcesOnly = TaskKey[File]("packageSourcesOnly", "Package the sources of the project")
+    val packageBinWithoutResources = TaskKey[File]("packageBinWithoutResources", "Like packageBin, but without the resources")
+    val packageSubmissionZip = TaskKey[File]("packageSubmissionZip")
+    val packageSubmission = inputKey[Unit]("package solution as an archive file")
+    val runGradingTests = taskKey[Unit]("run black-box tests used for final grading")
+  }
+
+
+  import autoImport._
+  import MOOCSettings.autoImport._
+
+  override lazy val projectSettings = Seq(
+    packageSubmissionSetting,
+    // submitSetting,
+    runGradingTestsSettings,
+
+    fork := true,
+    connectInput in run := true,
+    outputStrategy := Some(StdoutOutput),
+  ) ++ packageSubmissionZipSettings
+
+  lazy val runGradingTestsSettings = runGradingTests := {
+    val testSuiteJar = "grading-tests.jar"
+    if (!new File(testSuiteJar).exists) {
+      throw new MessageOnlyException(s"Could not find tests JarFile: $testSuiteJar")
+    }
+
+    val classPath = s"${(Test / dependencyClasspath).value.map(_.data).mkString(File.pathSeparator)}${File.pathSeparator}$testSuiteJar"
+    val junitProcess =
+      Fork.java.fork(
+        ForkOptions(),
+        "-cp" :: classPath ::
+        "org.junit.runner.JUnitCore" ::
+        (Test / testSuite).value ::
+        Nil
+      )
+
+    // Wait for tests to complete.
+    junitProcess.exitValue()
+  }
+
+
+  /** **********************************************************
+    * SUBMITTING A SOLUTION TO COURSERA
+    */
+
+  val packageSubmissionZipSettings = Seq(
+    packageSubmissionZip := {
+      val submission = crossTarget.value / "submission.zip"
+      val sources = (packageSourcesOnly in Compile).value
+      val binaries = (packageBinWithoutResources in Compile).value
+      IO.zip(Seq(sources -> "sources.zip", binaries -> "binaries.jar"), submission)
+      submission
+    },
+    artifactClassifier in packageSourcesOnly := Some("sources"),
+    artifact in (Compile, packageBinWithoutResources) ~= (art => art.withName(art.name + "-without-resources"))
+  ) ++
+  inConfig(Compile)(
+    Defaults.packageTaskSettings(packageSourcesOnly, Defaults.sourceMappings) ++
+    Defaults.packageTaskSettings(packageBinWithoutResources, Def.task {
+      val relativePaths =
+        (unmanagedResources in Compile).value.flatMap(Path.relativeTo((unmanagedResourceDirectories in Compile).value)(_))
+      (mappings in (Compile, packageBin)).value.filterNot { case (_, path) => relativePaths.contains(path) }
+    })
+  )
+
+  val maxSubmitFileSize = {
+    val mb = 1024 * 1024
+    10 * mb
+  }
+
+  /** Check that the jar exists, isn't empty, isn't crazy big, and can be read
+    * If so, encode jar as base64 so we can send it to Coursera
+    */
+  def prepareJar(jar: File, s: TaskStreams): String = {
+    val errPrefix = "Error submitting assignment jar: "
+    val fileLength = jar.length()
+    if (!jar.exists()) {
+      s.log.error(errPrefix + "jar archive does not exist\n" + jar.getAbsolutePath)
+      failSubmit()
+    } else if (fileLength == 0L) {
+      s.log.error(errPrefix + "jar archive is empty\n" + jar.getAbsolutePath)
+      failSubmit()
+    } else if (fileLength > maxSubmitFileSize) {
+      s.log.error(errPrefix + "jar archive is too big. Allowed size: " +
+        maxSubmitFileSize + " bytes, found " + fileLength + " bytes.\n" +
+        jar.getAbsolutePath)
+      failSubmit()
+    } else {
+      val bytes = new Array[Byte](fileLength.toInt)
+      val sizeRead = try {
+        val is = new FileInputStream(jar)
+        val read = is.read(bytes)
+        is.close()
+        read
+      } catch {
+        case ex: IOException =>
+          s.log.error(errPrefix + "failed to read sources jar archive\n" + ex.toString)
+          failSubmit()
+      }
+      if (sizeRead != bytes.length) {
+        s.log.error(errPrefix + "failed to read the sources jar archive, size read: " + sizeRead)
+        failSubmit()
+      } else encodeBase64(bytes)
+    }
+  }
+
+  /** Task to package solution to a given file path */
+  lazy val packageSubmissionSetting = packageSubmission := {
+    val args: Seq[String] = Def.spaceDelimited("[path]").parsed
+    val s: TaskStreams = streams.value // for logging
+    val jar = (packageSubmissionZip in Compile).value
+
+    val base64Jar = prepareJar(jar, s)
+
+    val path = args.headOption.getOrElse((baseDirectory.value / "submission.jar").absolutePath)
+    scala.tools.nsc.io.File(path).writeAll(base64Jar)
+  }
+
+/*
+  /** Task to submit a solution to coursera */
+  val submit = inputKey[Unit]("submit solution to Coursera")
+  lazy val submitSetting = submit := {
+    // Fail if scalafix linting does not pass.
+    scalafixLinting.value
+
+    val args: Seq[String] = Def.spaceDelimited("<arg>").parsed
+    val s: TaskStreams = streams.value // for logging
+    val jar = (packageSubmissionZip in Compile).value
+
+    val assignmentDetails =
+      courseraId.?.value.getOrElse(throw new MessageOnlyException("This assignment can not be submitted to Coursera because the `courseraId` setting is undefined"))
+    val assignmentKey = assignmentDetails.key
+    val courseName =
+      course.value match {
+        case "capstone" => "scala-capstone"
+        case "bigdata"  => "scala-spark-big-data"
+        case other      => other
+      }
+
+    val partId = assignmentDetails.partId
+    val itemId = assignmentDetails.itemId
+    val premiumItemId = assignmentDetails.premiumItemId
+
+    val (email, secret) = args match {
+      case email :: secret :: Nil =>
+        (email, secret)
+      case _ =>
+        val inputErr =
+          s"""|Invalid input to `submit`. The required syntax for `submit` is:
+              |submit <email-address> <submit-token>
+              |
+              |The submit token is NOT YOUR LOGIN PASSWORD.
+              |It can be obtained from the assignment page:
+              |https://www.coursera.org/learn/$courseName/programming/$itemId
+              |${
+                premiumItemId.fold("") { id =>
+                  s"""or (for premium learners):
+                     |https://www.coursera.org/learn/$courseName/programming/$id
+                   """.stripMargin
+                }
+              }
+          """.stripMargin
+        s.log.error(inputErr)
+        failSubmit()
+    }
+
+    val base64Jar = prepareJar(jar, s)
+    val json =
+      s"""|{
+          |   "assignmentKey":"$assignmentKey",
+          |   "submitterEmail":"$email",
+          |   "secret":"$secret",
+          |   "parts":{
+          |      "$partId":{
+          |         "output":"$base64Jar"
+          |      }
+          |   }
+          |}""".stripMargin
+
+    def postSubmission[T](data: String): Try[HttpResponse[String]] = {
+      val http = Http("https://www.coursera.org/api/onDemandProgrammingScriptSubmissions.v1")
+      val hs = List(
+        ("Cache-Control", "no-cache"),
+        ("Content-Type", "application/json")
+      )
+      s.log.info("Connecting to Coursera...")
+      val response = Try(http.postData(data)
+                         .headers(hs)
+                         .option(HttpOptions.connTimeout(10000)) // scalaj default timeout is only 100ms, changing that to 10s
+                         .asString) // kick off HTTP POST
+      response
+    }
+
+    val connectMsg =
+      s"""|Attempting to submit "${assignment.value}" assignment in "$courseName" course
+          |Using:
+          |- email: $email
+          |- submit token: $secret""".stripMargin
+    s.log.info(connectMsg)
+
+    def reportCourseraResponse(response: HttpResponse[String]): Unit = {
+      val code = response.code
+      val respBody = response.body
+
+       /* Sample JSON response from Coursera
+      {
+        "message": "Invalid email or token.",
+        "details": {
+          "learnerMessage": "Invalid email or token."
+        }
+      }
+      */
+
+      // Success, Coursera responds with 2xx HTTP status code
+      if (response.is2xx) {
+        val successfulSubmitMsg =
+          s"""|Successfully connected to Coursera. (Status $code)
+              |
+                |Assignment submitted successfully!
+              |
+                |You can see how you scored by going to:
+              |https://www.coursera.org/learn/$courseName/programming/$itemId/
+              |${
+            premiumItemId.fold("") { id =>
+              s"""or (for premium learners):
+                 |https://www.coursera.org/learn/$courseName/programming/$id
+                       """.stripMargin
+            }
+          }
+              |and clicking on "My Submission".""".stripMargin
+        s.log.info(successfulSubmitMsg)
+      }
+
+      // Failure, Coursera responds with 4xx HTTP status code (client-side failure)
+      else if (response.is4xx) {
+        val result = Try(Json.parse(respBody)).toOption
+        val learnerMsg = result match {
+          case Some(resp: JsObject) =>
+            (JsPath \ "details" \ "learnerMessage").read[String].reads(resp).get
+          case Some(x) => // shouldn't happen
+            "Could not parse Coursera's response:\n" + x
+          case None =>
+            "Could not parse Coursera's response:\n" + respBody
+        }
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |There was something wrong while attempting to submit.
+              |Coursera says:
+              |$learnerMsg (Status $code)""".stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+
+      // Failure, Coursera responds with 5xx HTTP status code (server-side failure)
+      else if (response.is5xx) {
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |Coursera seems to be unavailable at the moment (Status $code)
+              |Check https://status.coursera.org/ and try again in a few minutes.
+           """.stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+
+      // Failure, Coursera repsonds with an unexpected status code
+      else {
+        val failedSubmitMsg =
+          s"""|Submission failed.
+              |Coursera replied with an unexpected code (Status $code)
+           """.stripMargin
+        s.log.error(failedSubmitMsg)
+      }
+    }
+
+    // kick it all off, actually make request
+    postSubmission(json) match {
+      case Success(resp) => reportCourseraResponse(resp)
+      case Failure(e) =>
+        val failedConnectMsg =
+          s"""|Connection to Coursera failed.
+              |There was something wrong while attempting to connect to Coursera.
+              |Check your internet connection.
+              |${e.toString}""".stripMargin
+        s.log.error(failedConnectMsg)
+    }
+
+   }
+*/
+
+  def failSubmit(): Nothing = {
+    sys.error("Submission failed")
+  }
+
+  /**
+    * *****************
+    * DEALING WITH JARS
+    */
+  def encodeBase64(bytes: Array[Byte]): String =
+    new String(Base64.encodeBase64(bytes))
+}

project/build.properties

@@ -0,0 +1 @@
+sbt.version=1.3.8

project/buildSettings.sbt

@@ -0,0 +1,5 @@
+// Used for Coursera submission (StudentPlugin)
+// libraryDependencies += "org.scalaj" %% "scalaj-http" % "2.4.2"
+// libraryDependencies += "com.typesafe.play" %% "play-json" % "2.7.4"
+// Used for Base64 (StudentPlugin)
+libraryDependencies += "commons-codec" % "commons-codec" % "1.10"

project/plugins.sbt

@@ -0,0 +1,2 @@
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.28")
+addSbtPlugin("ch.epfl.lamp" % "sbt-dotty" % "0.4.0")

src/main/scala/actorbintree/BinaryTreeSet.scala

@@ -0,0 +1,118 @@
+/**
+ * Copyright (C) 2009-2013 Typesafe Inc. <http://www.typesafe.com>
+ */
+package actorbintree
+
+import akka.actor._
+import scala.collection.immutable.Queue
+
+object BinaryTreeSet {
+
+  trait Operation {
+    def requester: ActorRef
+    def id: Int
+    def elem: Int
+  }
+
+  trait OperationReply {
+    def id: Int
+  }
+
+  /** Request with identifier `id` to insert an element `elem` into the tree.
+    * The actor at reference `requester` should be notified when this operation
+    * is completed.
+    */
+  case class Insert(requester: ActorRef, id: Int, elem: Int) extends Operation
+
+  /** Request with identifier `id` to check whether an element `elem` is present
+    * in the tree. The actor at reference `requester` should be notified when
+    * this operation is completed.
+    */
+  case class Contains(requester: ActorRef, id: Int, elem: Int) extends Operation
+
+  /** Request with identifier `id` to remove the element `elem` from the tree.
+    * The actor at reference `requester` should be notified when this operation
+    * is completed.
+    */
+  case class Remove(requester: ActorRef, id: Int, elem: Int) extends Operation
+
+  /** Request to perform garbage collection */
+  case object GC
+
+  /** Holds the answer to the Contains request with identifier `id`.
+    * `result` is true if and only if the element is present in the tree.
+    */
+  case class ContainsResult(id: Int, result: Boolean) extends OperationReply
+
+  /** Message to signal successful completion of an insert or remove operation. */
+  case class OperationFinished(id: Int) extends OperationReply
+
+}
+
+
+class BinaryTreeSet extends Actor {
+  import BinaryTreeSet._
+  import BinaryTreeNode._
+
+  def createRoot: ActorRef = context.actorOf(BinaryTreeNode.props(0, initiallyRemoved = true))
+
+  var root = createRoot
+
+  // optional (used to stash incoming operations during garbage collection)
+  var pendingQueue = Queue.empty[Operation]
+
+  // optional
+  def receive = normal
+
+  // optional
+  /** Accepts `Operation` and `GC` messages. */
+  val normal: Receive = { case _ => ??? }
+
+  // optional
+  /** Handles messages while garbage collection is performed.
+    * `newRoot` is the root of the new binary tree where we want to copy
+    * all non-removed elements into.
+    */
+  def garbageCollecting(newRoot: ActorRef): Receive = ???
+
+}
+
+object BinaryTreeNode {
+  trait Position
+
+  case object Left extends Position
+  case object Right extends Position
+
+  case class CopyTo(treeNode: ActorRef)
+  /**
+   * Acknowledges that a copy has been completed. This message should be sent
+   * from a node to its parent, when this node and all its children nodes have
+   * finished being copied.
+   */
+  case object CopyFinished
+
+  def props(elem: Int, initiallyRemoved: Boolean) = Props(classOf[BinaryTreeNode],  elem, initiallyRemoved)
+}
+
+class BinaryTreeNode(val elem: Int, initiallyRemoved: Boolean) extends Actor {
+  import BinaryTreeNode._
+  import BinaryTreeSet._
+
+  var subtrees = Map[Position, ActorRef]()
+  var removed = initiallyRemoved
+
+  // optional
+  def receive = normal
+
+  // optional
+  /** Handles `Operation` messages and `CopyTo` requests. */
+  val normal: Receive = { case _ => ??? }
+
+  // optional
+  /** `expected` is the set of ActorRefs whose replies we are waiting for,
+    * `insertConfirmed` tracks whether the copy of this node to the new tree has been confirmed.
+    */
+  def copying(expected: Set[ActorRef], insertConfirmed: Boolean): Receive = ???
+
+
+}

src/test/scala/actorbintree/BinaryTreeSuite.scala

@@ -0,0 +1,126 @@
+/**
+ * Copyright (C) 2009-2015 Typesafe Inc. <http://www.typesafe.com>
+ */
+package actorbintree
+
+import akka.actor.{ActorRef, ActorSystem, Props, actorRef2Scala, scala2ActorRef}
+import akka.testkit.{ImplicitSender, TestKit, TestProbe}
+import org.junit.Test
+import org.junit.Assert._
+
+import scala.util.Random
+import scala.concurrent.duration._
+
+class BinaryTreeSuite extends TestKit(ActorSystem("BinaryTreeSuite")) with ImplicitSender {
+
+  import actorbintree.BinaryTreeSet._
+
+  def receiveN(requester: TestProbe, ops: Seq[Operation], expectedReplies: Seq[OperationReply]): Unit =
+    requester.within(5.seconds) {
+      val repliesUnsorted = for (i <- 1 to ops.size) yield try {
+        requester.expectMsgType[OperationReply]
+      } catch {
+        case ex: Throwable if ops.size > 10 => sys.error(s"failure to receive confirmation $i/${ops.size}\n$ex")
+        case ex: Throwable                  => sys.error(s"failure to receive confirmation $i/${ops.size}\nRequests:" + ops.mkString("\n    ", "\n     ", "") + s"\n$ex")
+      }
+      val replies = repliesUnsorted.sortBy(_.id)
+      if (replies != expectedReplies) {
+        val pairs = (replies zip expectedReplies).zipWithIndex filter (x => x._1._1 != x._1._2)
+        fail("unexpected replies:" + pairs.map(x => s"at index ${x._2}: got ${x._1._1}, expected ${x._1._2}").mkString("\n    ", "\n    ", ""))
+      }
+    }
+
+  def verify(probe: TestProbe, ops: Seq[Operation], expected: Seq[OperationReply]): Unit = {
+    val topNode = system.actorOf(Props[BinaryTreeSet])
+
+    ops foreach { op =>
+      topNode ! op
+    }
+
+    receiveN(probe, ops, expected)
+    // the grader also verifies that enough actors are created
+  }
+
+  @Test def `proper inserts and lookups (5pts)`(): Unit = {
+    val topNode = system.actorOf(Props[BinaryTreeSet])
+
+    topNode ! Contains(testActor, id = 1, 1)
+    expectMsg(ContainsResult(1, false))
+
+    topNode ! Insert(testActor, id = 2, 1)
+    topNode ! Contains(testActor, id = 3, 1)
+
+    expectMsg(OperationFinished(2))
+    expectMsg(ContainsResult(3, true))
+    ()
+  }
+
+  @Test def `instruction example (5pts)`(): Unit = {
+    val requester = TestProbe()
+    val requesterRef = requester.ref
+    val ops = List(
+      Insert(requesterRef, id=100, 1),
+      Contains(requesterRef, id=50, 2),
+      Remove(requesterRef, id=10, 1),
+      Insert(requesterRef, id=20, 2),
+      Contains(requesterRef, id=80, 1),
+      Contains(requesterRef, id=70, 2)
+    )
+
+    val expectedReplies = List(
+      OperationFinished(id=10),
+      OperationFinished(id=20),
+      ContainsResult(id=50, false),
+      ContainsResult(id=70, true),
+      ContainsResult(id=80, false),
+      OperationFinished(id=100)
+    )
+
+    verify(requester, ops, expectedReplies)
+  }
+
+
+  @Test def `behave identically to built-in set (includes GC) (40pts)`(): Unit = {
+    val rnd = new Random()
+    def randomOperations(requester: ActorRef, count: Int): Seq[Operation] = {
+      def randomElement: Int = rnd.nextInt(100)
+      def randomOperation(requester: ActorRef, id: Int): Operation = rnd.nextInt(4) match {
+        case 0 => Insert(requester, id, randomElement)
+        case 1 => Insert(requester, id, randomElement)
+        case 2 => Contains(requester, id, randomElement)
+        case 3 => Remove(requester, id, randomElement)
+      }
+
+      for (seq <- 0 until count) yield randomOperation(requester, seq)
+    }
+
+    def referenceReplies(operations: Seq[Operation]): Seq[OperationReply] = {
+      var referenceSet = Set.empty[Int]
+      def replyFor(op: Operation): OperationReply = op match {
+        case Insert(_, seq, elem) =>
+          referenceSet = referenceSet + elem
+          OperationFinished(seq)
+        case Remove(_, seq, elem) =>
+          referenceSet = referenceSet - elem
+          OperationFinished(seq)
+        case Contains(_, seq, elem) =>
+          ContainsResult(seq, referenceSet(elem))
+      }
+
+      for (op <- operations) yield replyFor(op)
+    }
+
+    val requester = TestProbe()
+    val topNode = system.actorOf(Props[BinaryTreeSet])
+    val count = 1000
+
+    val ops = randomOperations(requester.ref, count)
+    val expectedReplies = referenceReplies(ops)
+
+    ops foreach { op =>
+      topNode ! op
+      if (rnd.nextDouble() < 0.1) topNode ! GC
+    }
+    receiveN(requester, ops, expectedReplies)
+  }
+}