Persistence testkit implementation #15571 (#26825)

akka-docs/src/main/paradox/general/configuration-reference.md

@@ -62,6 +62,11 @@ nondeterministic when loading the configuration.`
 
 @@snip [reference.conf](/akka-persistence-query/src/main/resources/reference.conf)
 
+<a id="config-akka-persistence-testkit"></a>
+### akka-persistence-testkit
+
+@@snip [reference.conf](/akka-persistence-testkit/src/main/resources/reference.conf)
+
 <a id="config-akka-remote-artery"></a>
 ### akka-remote artery
 

akka-docs/src/main/paradox/persistence.md

@@ -804,7 +804,7 @@ to the application configuration. If not specified, an exception will be throw w
 
 For more advanced schema evolution techniques refer to the @ref:[Persistence - Schema Evolution](persistence-schema-evolution.md) documentation.
 
-## Testing
+## Testing with LevelDB journal
 
 When running tests with LevelDB default settings in `sbt`, make sure to set `fork := true` in your sbt project. Otherwise, you'll see an `UnsatisfiedLinkError`. Alternatively, you can switch to a LevelDB Java port by setting
 

akka-docs/src/main/paradox/typed/persistence-testing.md

@@ -65,6 +65,120 @@ Scala
 Java
 :  @@snip [AccountExampleDocTest.java](/akka-cluster-sharding-typed/src/test/java/jdocs/akka/cluster/sharding/typed/AccountExampleDocTest.java) { #test-events }
 
+## Persistence TestKit
+
+**Note!** The testkit is a new feature, api may have changes breaking source compatibility in future versions.
+
+Persistence testkit allows to check events saved in a storage, emulate storage operations and exceptions.
+To use the testkit you need to add the following dependency in your project:
+
+@@dependency[sbt,Maven,Gradle] {
+  group="com.typesafe.akka"
+  artifact="akka-persistence-testkit_$scala.binary_version$"
+  version="$akka.version$"
+}
+
+There are two testkit classes which have similar api:
+
+ * @apidoc[PersistenceTestKit] class is for events
+ * @apidoc[SnapshotTestKit] class is for snapshots
+ 
+The testkit classes have two corresponding plugins which emulate the behavior of the storages: 
+
+ * @apidoc[PersistenceTestKitPlugin] class emulates a events storage 
+ * @apidoc[PersistenceTestKitSnapshotPlugin] class emulates a snapshots storage
+
+**Note!** The corresponding plugins **must** be configured in the actor system which is used to initialize the particular testkit class:
+
+Scala
+:  @@snip [Configuration.scala](/akka-docs/src/test/scala/docs/persistence/testkit/Configuration.scala) { #testkit-typed-conf }
+
+Java
+:  @@snip [Configuration.java](/akka-docs/src/test/java/jdocs/persistence/testkit/Configuration.java) { #testkit-typed-conf }
+
+and
+
+Scala
+:  @@snip [Configuration.scala](/akka-docs/src/test/scala/docs/persistence/testkit/Configuration.scala) { #snapshot-typed-conf }
+
+Java
+:  @@snip [Configuration.java](/akka-docs/src/test/java/jdocs/persistence/testkit/Configuration.java) { #snapshot-typed-conf }
+
+A typical scenario is to create a persistent actor, send commands to it and check that it persists events as it is expected:
+
+Scala
+:  @@snip [TestKitExamples.scala](/akka-docs/src/test/scala/docs/persistence/testkit/TestKitExamples.scala) { #testkit-typed-usecase }
+
+Java
+:  @@snip [TestKitExamples.java](/akka-docs/src/test/java/jdocs/persistence/testkit/TestKitExamples.java) { #testkit-typed-usecase }
+
+You can safely use persistence testkit in combination with main akka testkit.
+
+The main methods of the api allow to (see @apidoc[PersistenceTestKit] and @apidoc[SnapshotTestKit] for more details):
+
+ * check if the given event/snapshot object is the next persisted in the storage.
+ * read a sequence of persisted events/snapshots.
+ * check that no events/snapshots have been persisted in the storage.
+ * throw the default exception from the storage on attempt to persist, read or delete the following event/snapshot.
+ * clear the events/snapshots persisted in the storage.
+ * reject the events, but not snapshots (rejections are not supported for snapshots in the original api).
+ * set your own [policy](#setting-your-own-policy-for-the-storage) which emulates the work of the storage. 
+Policy determines what to do when persistence needs to execute some operation on the storage (i.e. read, delete, etc.).
+ * get all the events/snapshots persisted in the storage
+ * put the events/snapshots in the storage to test recovery
+ 
+#### Setting your own policy for the storage
+
+You can implement and set your own policy for the storage to control its actions on particular operations, for example you can fail or reject events on your own conditions.
+Implement the @apidoc[ProcessingPolicy[EventStorage.JournalOperation]] @scala[trait]@java[interface] for event storage
+or @apidoc[ProcessingPolicy[SnapshotStorage.SnapshotOperation]] @scala[trait]@java[interface] for snapshot storage,
+and set it with `withPolicy()` method.
+
+`tryProcess()` method of the @apidoc[ProcessingPolicy] has two arguments: persistence id and the storage operation. 
+
+Event storage has the following operations:
+
+ * @apidoc[ReadEvents] Read the events from the storage.
+ * @apidoc[WriteEvents] Write the events to the storage.
+ * @apidoc[DeleteEvents] Delete the events from the storage.
+ * @apidoc[ReadSeqNum] Read the highest sequence number for particular persistence id.
+
+Snapshot storage has the following operations:
+
+ * @apidoc[ReadSnapshot] Read the snapshot from the storage.
+ * @apidoc[WriteSnapshot] Writhe the snapshot to the storage.
+ * @apidoc[DeleteSnapshotsByCriteria] Delete snapshots in the storage by criteria.
+ * @apidoc[DeleteSnapshotByMeta] Delete particular snapshot from the storage by its metadata.
+
+The `tryProcess()` method must return one of the processing results:
+ 
+ * @apidoc[ProcessingSuccess] Successful completion of the operation. All the events will be saved/read/deleted.
+ * @apidoc[StorageFailure] Emulates exception from the storage.
+ * @apidoc[Reject] Emulates rejection from the storage.
+
+**Note** that snapshot storage does not have rejections. If you return `Reject` in the `tryProcess()` of the snapshot storage policy, it will have the same effect as the `StorageFailure`.
+
+Here is an example of the policy for an event storage:
+
+Scala
+:  @@snip [TestKitExamples.scala](/akka-docs/src/test/scala/docs/persistence/testkit/TestKitExamples.scala) { #set-event-storage-policy }
+
+Java
+:  @@snip [TestKitExamples.java](/akka-docs/src/test/java/jdocs/persistence/testkit/TestKitExamples.java) { #set-event-storage-policy }
+
+Here is an example of the policy for a snapshot storage:
+
+Scala
+:  @@snip [TestKitExamples.scala](/akka-docs/src/test/scala/docs/persistence/testkit/TestKitExamples.scala) { #set-snapshot-storage-policy }
+
+Java
+:  @@snip [TestKitExamples.java](/akka-docs/src/test/java/jdocs/persistence/testkit/TestKitExamples.java) { #set-snapshot-storage-policy } 
+
+### Configuration of Persistence TestKit
+
+There are several configuration properties for persistence testkit, please refer
+to the @ref:[reference configuration](../general/configuration-reference.md#config-akka-persistence-testkit)
+
 ## Integration testing
 
 The in-memory journal and file based snapshot store can be used also for integration style testing of a single

akka-docs/src/test/java/jdocs/persistence/testkit/Configuration.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.persistence.testkit;
+
+import akka.actor.typed.ActorSystem;
+import akka.actor.typed.Behavior;
+import akka.persistence.testkit.PersistenceTestKitPlugin;
+import akka.persistence.testkit.PersistenceTestKitSnapshotPlugin;
+import akka.persistence.testkit.javadsl.PersistenceTestKit;
+import akka.persistence.testkit.javadsl.SnapshotTestKit;
+import com.typesafe.config.Config;
+import com.typesafe.config.ConfigFactory;
+
+public class Configuration {
+
+  // #testkit-typed-conf
+  public class PersistenceTestKitConfig {
+
+    Config conf =
+        PersistenceTestKitPlugin.getInstance()
+            .config()
+            .withFallback(ConfigFactory.defaultApplication());
+
+    ActorSystem<Command> system = ActorSystem.create(new SomeBehavior(), "example", conf);
+
+    PersistenceTestKit testKit = PersistenceTestKit.create(system);
+  }
+  // #testkit-typed-conf
+
+  // #snapshot-typed-conf
+  public class SnapshotTestKitConfig {
+
+    Config conf =
+        PersistenceTestKitSnapshotPlugin.getInstance()
+            .config()
+            .withFallback(ConfigFactory.defaultApplication());
+
+    ActorSystem<Command> system = ActorSystem.create(new SomeBehavior(), "example", conf);
+
+    SnapshotTestKit testKit = SnapshotTestKit.create(system);
+  }
+  // #snapshot-typed-conf
+
+}
+
+class SomeBehavior extends Behavior<Command> {
+  public SomeBehavior() {
+    super(1);
+  }
+}
+
+class Command {}

akka-docs/src/test/java/jdocs/persistence/testkit/TestKitExamples.java

@@ -0,0 +1,185 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package jdocs.persistence.testkit;
+
+import akka.actor.testkit.typed.javadsl.TestKitJunitResource;
+import akka.actor.typed.ActorRef;
+import akka.persistence.testkit.DeleteEvents;
+import akka.persistence.testkit.DeleteSnapshotByMeta;
+import akka.persistence.testkit.DeleteSnapshotsByCriteria;
+import akka.persistence.testkit.JournalOperation;
+import akka.persistence.testkit.PersistenceTestKitPlugin;
+import akka.persistence.testkit.ProcessingPolicy;
+import akka.persistence.testkit.ProcessingResult;
+import akka.persistence.testkit.ProcessingSuccess;
+import akka.persistence.testkit.ReadEvents;
+import akka.persistence.testkit.ReadSeqNum;
+import akka.persistence.testkit.ReadSnapshot;
+import akka.persistence.testkit.Reject;
+import akka.persistence.testkit.SnapshotOperation;
+import akka.persistence.testkit.StorageFailure;
+import akka.persistence.testkit.WriteEvents;
+import akka.persistence.testkit.WriteSnapshot;
+import akka.persistence.testkit.javadsl.PersistenceTestKit;
+import akka.persistence.typed.PersistenceId;
+import akka.persistence.typed.javadsl.CommandHandler;
+import akka.persistence.typed.javadsl.EventHandler;
+import akka.persistence.typed.javadsl.EventSourcedBehavior;
+import com.typesafe.config.ConfigFactory;
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Test;
+
+public class TestKitExamples {
+
+  // #set-event-storage-policy
+  class SampleEventStoragePolicy implements ProcessingPolicy<JournalOperation> {
+
+    // you can use internal state, it does not need to be thread safe
+    int count = 1;
+
+    @Override
+    public ProcessingResult tryProcess(String persistenceId, JournalOperation processingUnit) {
+      // check the type of operation and react with success or with reject or with failure.
+      // if you return ProcessingSuccess the operation will be performed, otherwise not.
+      if (count < 10) {
+        count += 1;
+        if (processingUnit instanceof ReadEvents) {
+          ReadEvents read = (ReadEvents) processingUnit;
+          if (read.batch().nonEmpty()) {
+            ProcessingSuccess.getInstance();
+          } else {
+            return StorageFailure.create();
+          }
+        } else if (processingUnit instanceof WriteEvents) {
+          return ProcessingSuccess.getInstance();
+        } else if (processingUnit instanceof DeleteEvents) {
+          return ProcessingSuccess.getInstance();
+        } else if (processingUnit.equals(ReadSeqNum.getInstance())) {
+          return Reject.create();
+        }
+        // you can set your own exception
+        return StorageFailure.create(new RuntimeException("your exception"));
+      } else {
+        return ProcessingSuccess.getInstance();
+      }
+    }
+  }
+  // #set-event-storage-policy
+
+  // #set-snapshot-storage-policy
+  class SnapshotStoragePolicy implements ProcessingPolicy<SnapshotOperation> {
+
+    // you can use internal state, it doesn't need to be thread safe
+    int count = 1;
+
+    @Override
+    public ProcessingResult tryProcess(String persistenceId, SnapshotOperation processingUnit) {
+      // check the type of operation and react with success or with failure.
+      // if you return ProcessingSuccess the operation will be performed, otherwise not.
+      if (count < 10) {
+        count += 1;
+        if (processingUnit instanceof ReadSnapshot) {
+          ReadSnapshot read = (ReadSnapshot) processingUnit;
+          if (read.getSnapshot().isPresent()) {
+            ProcessingSuccess.getInstance();
+          } else {
+            return StorageFailure.create();
+          }
+        } else if (processingUnit instanceof WriteSnapshot) {
+          return ProcessingSuccess.getInstance();
+        } else if (processingUnit instanceof DeleteSnapshotsByCriteria) {
+          return ProcessingSuccess.getInstance();
+        } else if (processingUnit instanceof DeleteSnapshotByMeta) {
+          return ProcessingSuccess.getInstance();
+        }
+        // you can set your own exception
+        return StorageFailure.create(new RuntimeException("your exception"));
+      } else {
+        return ProcessingSuccess.getInstance();
+      }
+    }
+  }
+  // #set-snapshot-storage-policy
+
+}
+
+// #testkit-typed-usecase
+class SampleTest {
+
+  @ClassRule
+  public static final TestKitJunitResource testKit =
+      new TestKitJunitResource(
+          PersistenceTestKitPlugin.getInstance()
+              .config()
+              .withFallback(ConfigFactory.defaultApplication()));
+
+  PersistenceTestKit persistenceTestKit = PersistenceTestKit.create(testKit.system());
+
+  @Before
+  void beforeAll() {
+    persistenceTestKit.clearAll();
+  }
+
+  @Test
+  void test() {
+    ActorRef<Cmd> ref =
+        testKit.spawn(new YourPersistentBehavior(PersistenceId.ofUniqueId("some-id")));
+
+    Cmd cmd = new Cmd("data");
+    ref.tell(cmd);
+    Evt expectedEventPersisted = new Evt(cmd.data);
+
+    persistenceTestKit.expectNextPersisted("your-persistence-id", expectedEventPersisted);
+  }
+}
+
+final class Cmd {
+
+  public final String data;
+
+  public Cmd(String data) {
+    this.data = data;
+  }
+}
+
+final class Evt {
+
+  public final String data;
+
+  public Evt(String data) {
+    this.data = data;
+  }
+}
+
+final class State {}
+
+class YourPersistentBehavior extends EventSourcedBehavior<Cmd, Evt, State> {
+
+  public YourPersistentBehavior(PersistenceId persistenceId) {
+    super(persistenceId);
+  }
+
+  @Override
+  public State emptyState() {
+    // some state
+    return new State();
+  }
+
+  @Override
+  public CommandHandler<Cmd, Evt, State> commandHandler() {
+    return newCommandHandlerBuilder()
+        .forAnyState()
+        .onCommand(Cmd.class, command -> Effect().persist(new Evt(command.data)))
+        .build();
+  }
+
+  @Override
+  public EventHandler<State, Evt> eventHandler() {
+    // TODO handle events
+    return newEventHandlerBuilder().build();
+  }
+}
+// #testkit-typed-usecase

akka-docs/src/test/scala/docs/persistence/testkit/Configuration.scala

@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package docs.persistence.testkit
+
+import akka.actor.typed.ActorSystem
+import akka.persistence.testkit.{ PersistenceTestKitPlugin, PersistenceTestKitSnapshotPlugin }
+import akka.persistence.testkit.scaladsl.{ PersistenceTestKit, SnapshotTestKit }
+import com.typesafe.config.ConfigFactory
+
+object TestKitTypedConf {
+
+  //#testkit-typed-conf
+
+  val yourConfiguration = ConfigFactory.defaultApplication()
+
+  val system =
+    ActorSystem(??? /*some behavior*/, "test-system", PersistenceTestKitPlugin.config.withFallback(yourConfiguration))
+
+  val testKit = PersistenceTestKit(system)
+
+  //#testkit-typed-conf
+
+}
+
+object SnapshotTypedConf {
+
+  //#snapshot-typed-conf
+
+  val yourConfiguration = ConfigFactory.defaultApplication()
+
+  val system = ActorSystem(
+    ??? /*some behavior*/,
+    "test-system",
+    PersistenceTestKitSnapshotPlugin.config.withFallback(yourConfiguration))
+
+  val testKit = SnapshotTestKit(system)
+
+  //#snapshot-typed-conf
+
+}

akka-docs/src/test/scala/docs/persistence/testkit/TestKitExamples.scala

@@ -0,0 +1,107 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package docs.persistence.testkit
+
+import akka.actor.typed.ActorSystem
+import akka.persistence.testkit._
+import akka.persistence.testkit.scaladsl.PersistenceTestKit
+import akka.persistence.typed.scaladsl.{ Effect, EventSourcedBehavior }
+import com.typesafe.config.ConfigFactory
+import org.scalatest.BeforeAndAfterAll
+import org.scalatest.wordspec.AnyWordSpecLike
+
+class TestKitExamples {
+
+  //#testkit-typed-usecase
+  class TypedSampleSpec extends AnyWordSpecLike with BeforeAndAfterAll {
+
+    val system: ActorSystem[Cmd] = ActorSystem(
+      EventSourcedBehavior[Cmd, Evt, State](
+        persistenceId = ???,
+        eventHandler = ???,
+        commandHandler = (_, cmd) => Effect.persist(Evt(cmd.data)),
+        emptyState = ???),
+      "name",
+      PersistenceTestKitPlugin.config.withFallback(ConfigFactory.defaultApplication()))
+    val persistenceTestKit = PersistenceTestKit(system)
+
+    override def beforeAll(): Unit =
+      persistenceTestKit.clearAll()
+
+    "Persistent actor" should {
+
+      "persist all events" in {
+
+        val persistentActor = system
+        val cmd = Cmd("data")
+
+        persistentActor ! cmd
+
+        val expectedPersistedEvent = Evt(cmd.data)
+        persistenceTestKit.expectNextPersisted("your-persistence-id", expectedPersistedEvent)
+      }
+
+    }
+  }
+  //#testkit-typed-usecase
+
+  //#set-event-storage-policy
+  class SampleEventStoragePolicy extends EventStorage.JournalPolicies.PolicyType {
+
+    //you can use internal state, it does not need to be thread safe
+    var count = 1
+
+    override def tryProcess(persistenceId: String, processingUnit: JournalOperation): ProcessingResult =
+      if (count < 10) {
+        count += 1
+        //check the type of operation and react with success or with reject or with failure.
+        //if you return ProcessingSuccess the operation will be performed, otherwise not.
+        processingUnit match {
+          case ReadEvents(batch) if batch.nonEmpty => ProcessingSuccess
+          case WriteEvents(batch) if batch.size > 1 =>
+            ProcessingSuccess
+          case ReadSeqNum      => StorageFailure()
+          case DeleteEvents(_) => Reject()
+          case _               => StorageFailure()
+        }
+      } else {
+        ProcessingSuccess
+      }
+
+  }
+  //#set-event-storage-policy
+
+  //#set-snapshot-storage-policy
+  class SampleSnapshotStoragePolicy extends SnapshotStorage.SnapshotPolicies.PolicyType {
+
+    //you can use internal state, it does not need to be thread safe
+    var count = 1
+
+    override def tryProcess(persistenceId: String, processingUnit: SnapshotOperation): ProcessingResult =
+      if (count < 10) {
+        count += 1
+        //check the type of operation and react with success or with reject or with failure.
+        //if you return ProcessingSuccess the operation will be performed, otherwise not.
+        processingUnit match {
+          case ReadSnapshot(_, payload) if payload.nonEmpty =>
+            ProcessingSuccess
+          case WriteSnapshot(meta, payload) if meta.sequenceNr > 10 =>
+            ProcessingSuccess
+          case DeleteSnapshotsByCriteria(_) => StorageFailure()
+          case DeleteSnapshotByMeta(meta) if meta.sequenceNr < 10 =>
+            ProcessingSuccess
+          case _ => StorageFailure()
+        }
+      } else {
+        ProcessingSuccess
+      }
+  }
+  //#set-snapshot-storage-policy
+
+}
+
+case class Cmd(data: String)
+case class Evt(data: String)
+trait State

akka-persistence-testkit/src/main/resources/reference.conf

@@ -0,0 +1,30 @@
+##################################################
+# Akka Persistence Testkit Reference Config File #
+##################################################
+
+# This is the reference config file that contains all the default settings.
+# Make your edits/overrides in your application.conf.
+
+akka.persistence.testkit {
+
+  # configuration for persistence testkit for events
+  events {
+    # enable serialization of the persisted events
+    serialize = true
+    # timeout for assertions
+    assert-timeout = 3s
+    # poll interval for assertions with timeout
+    assert-poll-interval = 100millis
+  }
+
+  # configuration for persistence testkit for snapshots
+  snapshots {
+    # enable serialization of the persisted snapshots
+    serialize = true
+    # timeout for assertions
+    assert-timeout = 3s
+    # poll interval for assertions with timeout
+    assert-poll-interval = 100millis
+  }
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/EventStorage.scala

@@ -0,0 +1,156 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit
+
+import akka.annotation.InternalApi
+import akka.persistence.PersistentRepr
+import akka.persistence.testkit.ProcessingPolicy.DefaultPolicies
+import akka.persistence.testkit.internal.TestKitStorage
+import akka.util.ccompat.JavaConverters._
+import java.util.{ List => JList }
+
+import scala.collection.immutable
+import scala.util.{ Failure, Success, Try }
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] trait EventStorage extends TestKitStorage[JournalOperation, PersistentRepr] {
+
+  import EventStorage._
+
+  def addAny(key: String, elem: Any): Unit =
+    addAny(key, immutable.Seq(elem))
+
+  def addAny(key: String, elems: immutable.Seq[Any]): Unit =
+    // need to use `updateExisting` because `mapAny` reads latest seqnum
+    // and therefore must be done at the same time with the update, not before
+    updateOrSetNew(key, v => v ++ mapAny(key, elems).toVector)
+
+  override def reprToSeqNum(repr: PersistentRepr): Long = repr.sequenceNr
+
+  def add(elems: immutable.Seq[PersistentRepr]): Unit =
+    elems.groupBy(_.persistenceId).foreach(gr => add(gr._1, gr._2))
+
+  override protected val DefaultPolicy = JournalPolicies.PassAll
+
+  /**
+   * @throws Exception from StorageFailure in the current writing policy
+   */
+  def tryAdd(elems: immutable.Seq[PersistentRepr]): Try[Unit] = {
+    val grouped = elems.groupBy(_.persistenceId)
+
+    val processed = grouped.map {
+      case (pid, els) => currentPolicy.tryProcess(pid, WriteEvents(els.map(_.payload)))
+    }
+
+    val reduced: ProcessingResult =
+      processed.foldLeft[ProcessingResult](ProcessingSuccess)((left: ProcessingResult, right: ProcessingResult) =>
+        (left, right) match {
+          case (ProcessingSuccess, ProcessingSuccess) => ProcessingSuccess
+          case (f: StorageFailure, _)                 => f
+          case (_, f: StorageFailure)                 => f
+          case (r: Reject, _)                         => r
+          case (_, r: Reject)                         => r
+        })
+
+    reduced match {
+      case ProcessingSuccess =>
+        add(elems)
+        Success(())
+      case Reject(ex)         => Failure(ex)
+      case StorageFailure(ex) => throw ex
+    }
+  }
+
+  def tryRead(
+      persistenceId: String,
+      fromSequenceNr: Long,
+      toSequenceNr: Long,
+      max: Long): immutable.Seq[PersistentRepr] = {
+    val batch = read(persistenceId, fromSequenceNr, toSequenceNr, max)
+    currentPolicy.tryProcess(persistenceId, ReadEvents(batch)) match {
+      case ProcessingSuccess  => batch
+      case Reject(ex)         => throw ex
+      case StorageFailure(ex) => throw ex
+    }
+  }
+
+  def tryReadSeqNumber(persistenceId: String): Long = {
+    currentPolicy.tryProcess(persistenceId, ReadSeqNum) match {
+      case ProcessingSuccess  => getHighestSeqNumber(persistenceId)
+      case Reject(ex)         => throw ex
+      case StorageFailure(ex) => throw ex
+    }
+  }
+
+  def tryDelete(persistenceId: String, toSeqNumber: Long): Unit = {
+    currentPolicy.tryProcess(persistenceId, DeleteEvents(toSeqNumber)) match {
+      case ProcessingSuccess  => deleteToSeqNumber(persistenceId, toSeqNumber)
+      case Reject(ex)         => throw ex
+      case StorageFailure(ex) => throw ex
+    }
+  }
+
+  private def mapAny(key: String, elems: immutable.Seq[Any]): immutable.Seq[PersistentRepr] = {
+    val sn = getHighestSeqNumber(key) + 1
+    elems.zipWithIndex.map(p => PersistentRepr(p._1, p._2 + sn, key))
+  }
+
+}
+
+object EventStorage {
+
+  object JournalPolicies extends DefaultPolicies[JournalOperation]
+
+}
+
+/**
+ * INTERNAL API
+ *
+ * Persistent journal operations.
+ */
+@InternalApi
+sealed trait JournalOperation
+
+/**
+ * Read from journal operation with events that were read.
+ */
+final case class ReadEvents(batch: immutable.Seq[Any]) extends JournalOperation {
+
+  def getBatch(): JList[Any] = batch.asJava
+
+}
+
+/**
+ * Write in journal operation with events to be written.
+ */
+final case class WriteEvents(batch: immutable.Seq[Any]) extends JournalOperation {
+
+  def getBatch(): JList[Any] = batch.asJava
+
+}
+
+/**
+ * Read persistent actor's sequence number operation.
+ */
+case object ReadSeqNum extends JournalOperation {
+
+  /**
+   * Java API: the singleton instance.
+   */
+  def getInstance() = this
+
+}
+
+/**
+ * Delete events in the journal up to `toSeqNumber` operation.
+ */
+final case class DeleteEvents(toSeqNumber: Long) extends JournalOperation {
+
+  def getToSeqNumber() = toSeqNumber
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/PersistenceTestKitPlugin.scala

@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit
+
+import akka.annotation.InternalApi
+import akka.persistence._
+import akka.persistence.journal.{ AsyncWriteJournal, Tagged }
+import akka.persistence.snapshot.SnapshotStore
+import akka.persistence.testkit.internal.{ InMemStorageExtension, SnapshotStorageEmulatorExtension }
+import com.typesafe.config.{ Config, ConfigFactory }
+
+import scala.collection.immutable
+import scala.concurrent.Future
+import scala.util.Try
+
+/**
+ * INTERNAL API
+ *
+ * Persistence testkit plugin for events.
+ */
+@InternalApi
+class PersistenceTestKitPlugin extends AsyncWriteJournal {
+
+  private final val storage = InMemStorageExtension(context.system)
+
+  override def asyncWriteMessages(messages: immutable.Seq[AtomicWrite]): Future[immutable.Seq[Try[Unit]]] =
+    Future.fromTry(Try(messages.map(aw => {
+      val data = aw.payload.map(pl =>
+        pl.payload match {
+          case Tagged(p, _) => pl.withPayload(p)
+          case _            => pl
+        })
+      storage.tryAdd(data)
+    })))
+
+  override def asyncDeleteMessagesTo(persistenceId: String, toSequenceNr: Long): Future[Unit] =
+    Future.fromTry(Try(storage.tryDelete(persistenceId, toSequenceNr)))
+
+  override def asyncReplayMessages(persistenceId: String, fromSequenceNr: Long, toSequenceNr: Long, max: Long)(
+      recoveryCallback: PersistentRepr => Unit): Future[Unit] =
+    Future.fromTry(Try(storage.tryRead(persistenceId, fromSequenceNr, toSequenceNr, max).foreach(recoveryCallback)))
+
+  override def asyncReadHighestSequenceNr(persistenceId: String, fromSequenceNr: Long): Future[Long] =
+    Future.fromTry(Try {
+      val found = storage.tryReadSeqNumber(persistenceId)
+      if (found < fromSequenceNr) fromSequenceNr else found
+    })
+
+}
+
+object PersistenceTestKitPlugin {
+
+  val PluginId = "akka.persistence.testkit.journal.pluginid"
+
+  import akka.util.ccompat.JavaConverters._
+
+  def getInstance() = this
+
+  val config: Config = ConfigFactory.parseMap(
+    Map(
+      "akka.persistence.journal.plugin" -> PluginId,
+      s"$PluginId.class" -> s"${classOf[PersistenceTestKitPlugin].getName}").asJava)
+
+}
+
+/**
+ * INTERNAL API
+ *
+ * Persistence testkit plugin for snapshots.
+ */
+@InternalApi
+class PersistenceTestKitSnapshotPlugin extends SnapshotStore {
+
+  private final val storage = SnapshotStorageEmulatorExtension(context.system)
+
+  override def loadAsync(persistenceId: String, criteria: SnapshotSelectionCriteria): Future[Option[SelectedSnapshot]] =
+    Future.fromTry(Try(storage.tryRead(persistenceId, criteria)))
+
+  override def saveAsync(metadata: SnapshotMetadata, snapshot: Any): Future[Unit] =
+    Future.fromTry(Try(storage.tryAdd(metadata, snapshot)))
+
+  override def deleteAsync(metadata: SnapshotMetadata): Future[Unit] =
+    Future.fromTry(Try(storage.tryDelete(metadata)))
+
+  override def deleteAsync(persistenceId: String, criteria: SnapshotSelectionCriteria): Future[Unit] =
+    Future.successful(Try(storage.tryDelete(persistenceId, criteria)))
+
+}
+
+object PersistenceTestKitSnapshotPlugin {
+
+  val PluginId = "akka.persistence.testkit.snapshotstore.pluginid"
+
+  import akka.util.ccompat.JavaConverters._
+
+  def getInstance() = this
+
+  val config: Config = ConfigFactory.parseMap(
+    Map(
+      "akka.persistence.snapshot-store.plugin" -> PluginId,
+      s"$PluginId.class" -> classOf[PersistenceTestKitSnapshotPlugin].getName).asJava)
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/ProcessingPolicy.scala

@@ -0,0 +1,195 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit
+
+import akka.annotation.{ ApiMayChange, InternalApi }
+
+/**
+ * Policies allow to emulate behavior of the storage (failures and rejections).
+ *
+ * @tparam U type determines operations which storage can perform.
+ */
+@ApiMayChange
+trait ProcessingPolicy[U] {
+
+  /**
+   * Emulates behavior of the storage.
+   * The function is invoked when any of the plugin's operations is executed.
+   * If you need this operation to succeed return [[ProcessingSuccess]],
+   * otherwise you should return some of the [[ProcessingFailure]]'s.
+   *
+   * @param processingUnit details about current operation to be executed
+   * @return needed result of processing the operation
+   */
+  def tryProcess(persistenceId: String, processingUnit: U): ProcessingResult
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+object ProcessingPolicy {
+
+  /**
+   * INTERNAL API
+   */
+  @InternalApi
+  private[testkit] trait DefaultPolicies[U] {
+
+    type PolicyType = ProcessingPolicy[U]
+
+    case object PassAll extends PolicyType {
+
+      override def tryProcess(persistenceId: String, processingUnit: U): ProcessingResult = ProcessingSuccess
+
+    }
+
+    class RejectNextNCond(
+        _numberToFail: Int,
+        _failureException: Throwable,
+        cond: (String, U) => Boolean,
+        onLimitExceed: => Unit = ())
+        extends CountNextNCond(_numberToFail, Reject(_failureException), ProcessingSuccess, cond, onLimitExceed)
+
+    class FailNextNCond(
+        _numberToFail: Int,
+        _failureException: Throwable,
+        cond: (String, U) => Boolean,
+        onLimitExceed: => Unit = ())
+        extends CountNextNCond(_numberToFail, StorageFailure(_failureException), ProcessingSuccess, cond, onLimitExceed)
+
+    class FailNextN(_numberToFail: Int, _failureException: Throwable, onLimitExceed: => Unit = ())
+        extends CountNextNCond(
+          _numberToFail,
+          StorageFailure(_failureException),
+          ProcessingSuccess,
+          (_, _) => true,
+          onLimitExceed)
+
+    class RejectNextN(_numberToReject: Int, _rejectionException: Throwable, onLimitExceed: => Unit = ())
+        extends CountNextNCond(
+          _numberToReject,
+          Reject(_rejectionException),
+          ProcessingSuccess,
+          (_, _) => true,
+          onLimitExceed)
+
+    class ReturnAfterNextNCond(
+        returnOnTrigger: => ProcessingResult,
+        returnNonTrigger: => ProcessingResult,
+        cond: (String, U) => Boolean)
+        extends PolicyType {
+
+      override def tryProcess(persistenceId: String, processingUnit: U): ProcessingResult = {
+        if (cond(persistenceId, processingUnit)) {
+          returnOnTrigger
+        } else {
+          returnNonTrigger
+        }
+      }
+
+    }
+
+    class CountNextNCond(
+        numberToCount: Int,
+        returnOnTrigger: => ProcessingResult,
+        returnNonTrigger: => ProcessingResult,
+        cond: (String, U) => Boolean,
+        onLimitExceed: => Unit)
+        extends ReturnAfterNextNCond(returnOnTrigger, returnNonTrigger, new Function2[String, U, Boolean] {
+
+          var counter = 0
+
+          override def apply(persistenceId: String, v1: U): Boolean = {
+            val intRes = cond(persistenceId, v1)
+            if (intRes && counter < numberToCount) {
+              counter += 1
+              if (counter == numberToCount) onLimitExceed
+              intRes
+            } else {
+              false
+            }
+          }
+        })
+
+  }
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+sealed trait ProcessingResult
+
+sealed abstract class ProcessingSuccess extends ProcessingResult
+
+/**
+ * Emulates successful processing of some operation.
+ */
+case object ProcessingSuccess extends ProcessingSuccess {
+
+  def getInstance(): ProcessingSuccess = this
+
+}
+
+sealed trait ProcessingFailure extends ProcessingResult {
+
+  def error: Throwable
+
+}
+
+sealed abstract class ExpectedRejection extends Throwable
+
+object ExpectedRejection extends ExpectedRejection {
+
+  def getInstance(): ExpectedRejection = this
+
+}
+
+sealed abstract class ExpectedFailure extends Throwable
+
+object ExpectedFailure extends ExpectedFailure {
+
+  def getInstance(): ExpectedFailure = this
+
+}
+
+/**
+ * Emulates rejection of operation by the journal with `error` exception.
+ * Has the same meaning as `StorageFailure` for snapshot storage,
+ * because it does not support rejections.
+ */
+final case class Reject(error: Throwable = ExpectedRejection) extends ProcessingFailure {
+
+  def getError(): Throwable = error
+
+}
+
+object Reject {
+
+  def create(error: Throwable): Reject = Reject(error)
+
+  def create(): Reject = Reject(ExpectedRejection)
+
+}
+
+/**
+ * Emulates exception thrown by the storage on the attempt to perform some operation.
+ */
+final case class StorageFailure(error: Throwable = ExpectedFailure) extends ProcessingFailure {
+
+  def getError(): Throwable = error
+
+}
+
+object StorageFailure {
+
+  def create(error: Throwable): StorageFailure = StorageFailure(error)
+
+  def create(): StorageFailure = StorageFailure(ExpectedFailure)
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/SnapshotStorage.scala

@@ -0,0 +1,150 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit
+
+import akka.annotation.InternalApi
+import akka.persistence.{ SelectedSnapshot, SnapshotMetadata, SnapshotSelectionCriteria }
+import akka.persistence.testkit.ProcessingPolicy.DefaultPolicies
+import akka.persistence.testkit.internal.TestKitStorage
+
+import scala.util.Success
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] trait SnapshotStorage extends TestKitStorage[SnapshotOperation, (SnapshotMetadata, Any)] {
+
+  import SnapshotStorage._
+
+  override def reprToSeqNum(repr: (SnapshotMetadata, Any)): Long =
+    repr._1.sequenceNr
+
+  override protected val DefaultPolicy = SnapshotPolicies.PassAll
+
+  def tryAdd(meta: SnapshotMetadata, payload: Any): Unit = {
+    currentPolicy.tryProcess(meta.persistenceId, WriteSnapshot(SnapshotMeta(meta.sequenceNr, meta.timestamp), payload)) match {
+      case ProcessingSuccess =>
+        add(meta.persistenceId, (meta, payload))
+        Success(())
+      case f: ProcessingFailure => throw f.error
+
+    }
+  }
+
+  def tryRead(persistenceId: String, criteria: SnapshotSelectionCriteria): Option[SelectedSnapshot] = {
+    val selectedSnapshot =
+      read(persistenceId).flatMap(
+        _.reverseIterator.find(v => criteria.matches(v._1)).map(v => SelectedSnapshot(v._1, v._2)))
+    currentPolicy.tryProcess(persistenceId, ReadSnapshot(criteria, selectedSnapshot.map(_.snapshot))) match {
+      case ProcessingSuccess    => selectedSnapshot
+      case f: ProcessingFailure => throw f.error
+    }
+  }
+
+  def tryDelete(persistenceId: String, selectionCriteria: SnapshotSelectionCriteria): Unit = {
+    currentPolicy.tryProcess(persistenceId, DeleteSnapshotsByCriteria(selectionCriteria)) match {
+      case ProcessingSuccess =>
+        delete(persistenceId, v => selectionCriteria.matches(v._1))
+      case f: ProcessingFailure => throw f.error
+    }
+  }
+
+  def tryDelete(meta: SnapshotMetadata): Unit = {
+    currentPolicy.tryProcess(meta.persistenceId, DeleteSnapshotByMeta(SnapshotMeta(meta.sequenceNr, meta.timestamp))) match {
+      case ProcessingSuccess =>
+        delete(meta.persistenceId, _._1.sequenceNr == meta.sequenceNr)
+      case f: ProcessingFailure => throw f.error
+    }
+  }
+
+}
+
+object SnapshotStorage {
+
+  object SnapshotPolicies extends DefaultPolicies[SnapshotOperation]
+
+}
+
+/**
+ * Snapshot metainformation.
+ */
+final case class SnapshotMeta(sequenceNr: Long, timestamp: Long = 0L) {
+
+  def getSequenceNr() = sequenceNr
+
+  def getTimestamp() = timestamp
+
+}
+
+case object SnapshotMeta {
+
+  def create(sequenceNr: Long, timestamp: Long) =
+    SnapshotMeta(sequenceNr, timestamp)
+
+  def create(sequenceNr: Long) = SnapshotMeta(sequenceNr)
+
+}
+
+/**
+ * INTERNAL API
+ * Operations supported by snapshot plugin
+ */
+@InternalApi
+sealed trait SnapshotOperation
+
+/**
+ *
+ * Storage read operation for recovery of the persistent actor.
+ *
+ * @param criteria criteria with which snapshot is searched
+ * @param snapshot snapshot found by criteria
+ */
+final case class ReadSnapshot(criteria: SnapshotSelectionCriteria, snapshot: Option[Any]) extends SnapshotOperation {
+
+  def getSnapshotSelectionCriteria() = criteria
+
+  def getSnapshot(): java.util.Optional[Any] =
+    snapshot.map(java.util.Optional.of[Any]).getOrElse(java.util.Optional.empty[Any]())
+
+}
+
+/**
+ * Storage write operation to persist snapshot in the storage.
+ *
+ * @param metadata snapshot metadata
+ * @param snapshot snapshot payload
+ */
+final case class WriteSnapshot(metadata: SnapshotMeta, snapshot: Any) extends SnapshotOperation {
+
+  def getMetadata() = metadata
+
+  def getSnapshot() = snapshot
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+sealed abstract class DeleteSnapshot extends SnapshotOperation
+
+/**
+ * Delete snapshots from storage by criteria.
+ */
+final case class DeleteSnapshotsByCriteria(criteria: SnapshotSelectionCriteria) extends DeleteSnapshot {
+
+  def getCriteria() = criteria
+
+}
+
+/**
+ * Delete particular snapshot from storage by its metadata.
+ */
+final case class DeleteSnapshotByMeta(metadata: SnapshotMeta) extends DeleteSnapshot {
+
+  def getMetadata() = metadata
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/InMemStorageExtension.scala

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.actor.{ ActorSystem, ExtendedActorSystem, ExtensionId, ExtensionIdProvider }
+import akka.annotation.InternalApi
+import akka.persistence.testkit.scaladsl.PersistenceTestKit
+import akka.persistence.testkit.EventStorage
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] object InMemStorageExtension extends ExtensionId[EventStorage] with ExtensionIdProvider {
+
+  override def get(system: ActorSystem): EventStorage = super.get(system)
+
+  override def createExtension(system: ExtendedActorSystem) =
+    if (PersistenceTestKit.Settings(system).serialize) {
+      new SerializedEventStorageImpl(system)
+    } else {
+      new SimpleEventStorageImpl
+    }
+
+  override def lookup() = InMemStorageExtension
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/SerializedEventStorageImpl.scala

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.actor.{ ActorSystem, ExtendedActorSystem }
+import akka.annotation.InternalApi
+import akka.persistence.PersistentRepr
+import akka.persistence.testkit.EventStorage
+import akka.serialization.{ Serialization, SerializationExtension }
+
+import scala.util.Try
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] class SerializedEventStorageImpl(system: ActorSystem) extends EventStorage {
+
+  override type InternalRepr = (Int, Array[Byte])
+
+  private lazy val serialization = SerializationExtension(system)
+
+  /**
+   * @return (serializer id, serialized bytes)
+   */
+  override def toInternal(repr: PersistentRepr): (Int, Array[Byte]) =
+    Serialization.withTransportInformation(system.asInstanceOf[ExtendedActorSystem]) { () =>
+      val s = serialization.findSerializerFor(repr)
+      (s.identifier, s.toBinary(repr))
+    }
+
+  /**
+   * @param internal (serializer id, serialized bytes)
+   */
+  override def toRepr(internal: (Int, Array[Byte])): PersistentRepr =
+    serialization
+      .deserialize(internal._2, internal._1, PersistentRepr.Undefined)
+      .flatMap(r => Try(r.asInstanceOf[PersistentRepr]))
+      .get
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/SerializedSnapshotStorageImpl.scala

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.actor.{ ActorSystem, ExtendedActorSystem }
+import akka.annotation.InternalApi
+import akka.persistence.SnapshotMetadata
+import akka.persistence.testkit.SnapshotStorage
+import akka.serialization.{ Serialization, SerializationExtension, Serializers }
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] class SerializedSnapshotStorageImpl(system: ActorSystem) extends SnapshotStorage {
+
+  override type InternalRepr = (SnapshotMetadata, String, Int, Array[Byte])
+
+  private lazy val serialization = SerializationExtension(system)
+
+  override def toRepr(internal: (SnapshotMetadata, String, Int, Array[Byte])): (SnapshotMetadata, Any) =
+    (internal._1, serialization.deserialize(internal._4, internal._3, internal._2).get)
+
+  override def toInternal(repr: (SnapshotMetadata, Any)): (SnapshotMetadata, String, Int, Array[Byte]) =
+    Serialization.withTransportInformation(system.asInstanceOf[ExtendedActorSystem]) { () =>
+      val payload = repr._2.asInstanceOf[AnyRef]
+      val s = serialization.findSerializerFor(payload)
+      val manifest = Serializers.manifestFor(s, payload)
+      (repr._1, manifest, s.identifier, s.toBinary(payload))
+    }
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/SimpleEventStorageImpl.scala

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.annotation.InternalApi
+import akka.persistence._
+import akka.persistence.testkit.EventStorage
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] class SimpleEventStorageImpl extends EventStorage {
+
+  override type InternalRepr = PersistentRepr
+
+  override def toInternal(repr: PersistentRepr): PersistentRepr = repr
+
+  override def toRepr(internal: PersistentRepr): PersistentRepr = internal
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/SimpleSnapshotStorageImpl.scala

@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.annotation.InternalApi
+import akka.persistence.SnapshotMetadata
+import akka.persistence.testkit.SnapshotStorage
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] class SimpleSnapshotStorageImpl extends SnapshotStorage {
+
+  override type InternalRepr = (SnapshotMetadata, Any)
+
+  override def toRepr(internal: (SnapshotMetadata, Any)): (SnapshotMetadata, Any) = identity(internal)
+
+  override def toInternal(repr: (SnapshotMetadata, Any)): (SnapshotMetadata, Any) = identity(repr)
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/SnapshotStorageEmulatorExtension.scala

@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import akka.actor.{ ActorSystem, ExtendedActorSystem, Extension, ExtensionId, ExtensionIdProvider }
+import akka.annotation.InternalApi
+import akka.persistence.testkit.scaladsl.SnapshotTestKit
+import akka.persistence.testkit.SnapshotStorage
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] object SnapshotStorageEmulatorExtension extends ExtensionId[SnapshotStorage] with ExtensionIdProvider {
+
+  override def get(system: ActorSystem): SnapshotStorage = super.get(system)
+
+  override def createExtension(system: ExtendedActorSystem): SnapshotStorage =
+    if (SnapshotTestKit.Settings(system).serialize) {
+      new SerializedSnapshotStorageImpl(system)
+    } else {
+      new SimpleSnapshotStorageImpl
+    }
+
+  override def lookup(): ExtensionId[_ <: Extension] =
+    SnapshotStorageEmulatorExtension
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/internal/TestKitStorage.scala

@@ -0,0 +1,154 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.internal
+
+import java.util.concurrent.ConcurrentHashMap
+import java.util.concurrent.atomic.AtomicReference
+
+import akka.actor.Extension
+import akka.annotation.InternalApi
+import akka.persistence.testkit.ProcessingPolicy
+
+import scala.collection.immutable
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+sealed trait InternalReprSupport[R] {
+
+  type InternalRepr
+
+  private[testkit] def toInternal(repr: R): InternalRepr
+
+  private[testkit] def toRepr(internal: InternalRepr): R
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+sealed trait InMemStorage[K, R] extends InternalReprSupport[R] {
+
+  import scala.math._
+
+  private final val eventsMap: ConcurrentHashMap[K, (Long, Vector[InternalRepr])] =
+    new ConcurrentHashMap()
+
+  def reprToSeqNum(repr: R): Long
+
+  def findMany(key: K, fromInclusive: Int, maxNum: Int): Option[Vector[R]] =
+    read(key).flatMap(
+      value =>
+        if (value.size > fromInclusive)
+          Some(value.drop(fromInclusive).take(maxNum))
+        else None)
+
+  def findOneByIndex(key: K, index: Int): Option[R] =
+    Option(eventsMap.get(key))
+      .flatMap {
+        case (_, value) => if (value.size > index) Some(value(index)) else None
+      }
+      .map(toRepr)
+
+  def add(key: K, p: R): Unit =
+    add(key, List(p))
+
+  /**
+   * Adds elements ordered by seqnum, sets new seqnum as max(old, max(newElemsSeqNums)))
+   */
+  def add(key: K, elems: immutable.Seq[R]): Unit =
+    updateOrSetNew(key, v => v ++ elems)
+
+  /**
+   * Deletes elements preserving highest sequence number.
+   */
+  def delete(key: K, needsToBeDeleted: R => Boolean): Vector[R] =
+    updateOrSetNew(key, v => v.filterNot(needsToBeDeleted))
+
+  /**
+   * Sets new elements returned by updater ordered by seqnum. Sets new seqnum as max(old, max(newElemsFromUpdaterSeqNums))
+   */
+  def updateOrSetNew(key: K, updater: Vector[R] => Vector[R]): Vector[R] =
+    eventsMap
+      .compute(
+        key,
+        (_: K, value: (Long, Vector[InternalRepr])) => {
+          val (sn, elems) = if (value != null) value else (0L, Vector.empty)
+          val upd = updater(elems.map(toRepr)).sortBy(reprToSeqNum)
+          (max(getLastSeqNumber(upd), sn), upd.map(toInternal))
+        })
+      ._2
+      .map(toRepr)
+
+  def read(key: K): Option[Vector[R]] =
+    Option(eventsMap.get(key)).map(_._2.map(toRepr))
+
+  def clearAll(): Unit =
+    eventsMap.clear()
+
+  /**
+   * Removes key and the whole value including seqnum.
+   */
+  def removeKey(key: K): Vector[R] =
+    Option(eventsMap.remove(key)).map(_._2).getOrElse(Vector.empty).map(toRepr)
+
+  /**
+   * Reads elems within the range of seqnums.
+   */
+  def read(key: K, fromInclusive: Long, toInclusive: Long, maxNumber: Long): immutable.Seq[R] =
+    read(key)
+      .getOrElse(Vector.empty)
+      .dropWhile(reprToSeqNum(_) < fromInclusive)
+      // we dont need to read highestSeqNumber because it will in any case stop at it if toInclusive > highestSeqNumber
+      .takeWhile(reprToSeqNum(_) <= toInclusive)
+      .take(if (maxNumber > Int.MaxValue) Int.MaxValue else maxNumber.toInt)
+
+  def removePreservingSeqNumber(key: K): Unit =
+    updateOrSetNew(key, _ => Vector.empty)
+
+  def getHighestSeqNumber(key: K): Long =
+    Option(eventsMap.get(key)).map(_._1).getOrElse(0L)
+
+  def deleteToSeqNumber(key: K, toSeqNumberInclusive: Long): Unit =
+    updateOrSetNew(key, value => {
+      value.dropWhile(reprToSeqNum(_) <= toSeqNumberInclusive)
+    })
+
+  def clearAllPreservingSeqNumbers(): Unit =
+    eventsMap.forEachKey(1, removePreservingSeqNumber)
+
+  private def getLastSeqNumber(elems: immutable.Seq[R]): Long =
+    elems.lastOption.map(reprToSeqNum).getOrElse(0L)
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+sealed trait PolicyOps[U] {
+
+  type Policy = ProcessingPolicy[U]
+
+  protected val DefaultPolicy: Policy
+
+  private lazy val _processingPolicy: AtomicReference[Policy] =
+    new AtomicReference(DefaultPolicy)
+
+  def currentPolicy: Policy = _processingPolicy.get()
+
+  def setPolicy(policy: Policy): Unit = _processingPolicy.set(policy)
+
+  def returnDefaultPolicy(): Unit = setPolicy(DefaultPolicy)
+
+}
+
+/**
+ * INTERNAL API
+ */
+@InternalApi
+private[testkit] trait TestKitStorage[P, R] extends InMemStorage[String, R] with PolicyOps[P] with Extension

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/javadsl/PersistenceTestKit.scala

@@ -0,0 +1,446 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.ActorSystem
+import akka.persistence.testkit.scaladsl.{ PersistenceTestKit => ScalaTestKit }
+import akka.util.JavaDurationConverters._
+import akka.util.ccompat.JavaConverters._
+import java.time.Duration
+import java.util.{ List => JList }
+import java.util.{ function => jf }
+
+import akka.annotation.ApiMayChange
+import akka.persistence.testkit.{ EventStorage, ExpectedFailure, ExpectedRejection, JournalOperation }
+
+/**
+ * Class for testing persisted events in persistent actors.
+ */
+@ApiMayChange
+class PersistenceTestKit(system: ActorSystem) {
+
+  private val scalaTestkit = new ScalaTestKit(system)
+
+  /**
+   * Check that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String): Unit = scalaTestkit.expectNothingPersisted(persistenceId)
+
+  /**
+   * Check for `max` time that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String, max: Duration): Unit =
+    scalaTestkit.expectNothingPersisted(persistenceId, max.asScala)
+
+  /**
+   * Check that `event` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A): A =
+    scalaTestkit.expectNextPersisted(persistenceId, event)
+
+  /**
+   * Check for `max` time that `event` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A, max: Duration): A =
+    scalaTestkit.expectNextPersisted(persistenceId, event, max.asScala)
+
+  /**
+   * Check that next persisted in storage for particular persistence id event has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A]): A =
+    scalaTestkit.expectNextPersistedClass(persistenceId, cla)
+
+  /**
+   * Check for `max` time that next persisted in storage for particular persistence id event has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A], max: Duration): A =
+    scalaTestkit.expectNextPersistedClass(persistenceId, cla, max.asScala)
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNPersisted(persistenceId, n, cause)
+
+  /**
+   * Fail next `n` write operations for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int): Unit = failNextNPersisted(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNPersisted(n, cause)
+
+  /**
+   * Fail next `n` write operations with default exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int): Unit = failNextNPersisted(n, ExpectedFailure)
+
+  /**
+   * Fail next write operation with `cause` exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String, cause: Throwable): Unit = failNextNPersisted(persistenceId, 1, cause)
+
+  /**
+   * Fail next write operation with default exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String): Unit = failNextNPersisted(persistenceId, 1)
+
+  /**
+   * Fail next write operation event with `cause` exception for any persistence id.
+   */
+  def failNextPersisted(cause: Throwable): Unit = failNextNPersisted(1, cause)
+
+  /**
+   * Fail next write operation with default exception for any persistence id.
+   */
+  def failNextPersisted(): Unit = failNextNPersisted(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for any persistence id.
+   */
+  def failNextRead(cause: Throwable): Unit = failNextNReads(1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(): Unit = failNextNReads(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for particular persistence id.
+   */
+  def failNextRead(persistenceId: String, cause: Throwable): Unit = failNextNReads(persistenceId, 1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(persistenceId: String): Unit = failNextNReads(persistenceId, 1)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for any persistence id.
+   */
+  def failNextNReads(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNReads(n, cause)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for any persistence id.
+   */
+  def failNextNReads(n: Int): Unit = failNextNReads(n, ExpectedFailure)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNReads(persistenceId, n, cause)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int): Unit = failNextNReads(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for any persistence id.
+   */
+  def failNextDelete(cause: Throwable): Unit = failNextNDeletes(1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for any persistence id.
+   */
+  def failNextDelete(): Unit = failNextNDeletes(1)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String, cause: Throwable): Unit = failNextNDeletes(persistenceId, 1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String): Unit = failNextNDeletes(persistenceId, 1)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNDeletes(n, cause)
+
+  /**
+   * Fail next n delete from storage attempts with default exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int): Unit = failNextNDeletes(n, ExpectedFailure)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNDeletes(persistenceId, n, cause)
+
+  /**
+   * Fail next n delete from storage attempts with default exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int): Unit = failNextNDeletes(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Receive next n events from the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A]): JList[A] =
+    scalaTestkit.receivePersisted(persistenceId, n, cla).asJava
+
+  /**
+   * Receive for `max` time next n events from the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A], max: Duration): JList[A] =
+    scalaTestkit.receivePersisted(persistenceId, n, cla, max.asScala).asJava
+
+  /**
+   * Reject next n save in storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.rejectNextNPersisted(persistenceId, n, cause)
+
+  /**
+   * Reject next n save in storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNPersisted(persistenceId: String, n: Int): Unit =
+    rejectNextNPersisted(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n save in storage operations for any persistence id with default exception.
+   */
+  def rejectNextNPersisted(n: Int): Unit = rejectNextNPersisted(n, ExpectedRejection)
+
+  /**
+   * Reject next n save in storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNPersisted(n: Int, cause: Throwable): Unit = scalaTestkit.rejectNextNPersisted(n, cause)
+
+  /**
+   * Reject next save in storage operation for particular persistence id with default exception.
+   */
+  def rejectNextPersisted(persistenceId: String): Unit = rejectNextNPersisted(persistenceId, 1)
+
+  /**
+   * Reject next save in storage operation for particular persistence id with `cause` exception.
+   */
+  def rejectNextPersisted(persistenceId: String, cause: Throwable): Unit = rejectNextNPersisted(persistenceId, 1, cause)
+
+  /**
+   * Reject next save in storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextPersisted(cause: Throwable): Unit = rejectNextNPersisted(1, cause)
+
+  /**
+   * Reject next save in storage operation for any persistence id with default exception.
+   */
+  def rejectNextPersisted(): Unit = rejectNextNPersisted(1)
+
+  /**
+   * Reject next read from storage operation for any persistence id with default exception.
+   */
+  def rejectNextRead(): Unit = rejectNextNReads(1)
+
+  /**
+   * Reject next read from storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextRead(cause: Throwable): Unit = rejectNextNReads(1, cause)
+
+  /**
+   * Reject next n read from storage operations for any persistence id with default exception.
+   */
+  def rejectNextNReads(n: Int): Unit = rejectNextNReads(n, ExpectedRejection)
+
+  /**
+   * Reject next n read from storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNReads(n: Int, cause: Throwable): Unit = scalaTestkit.rejectNextNReads(n, cause)
+
+  /**
+   * Reject next read from storage operation for particular persistence id with default exception.
+   */
+  def rejectNextRead(persistenceId: String): Unit = rejectNextNReads(persistenceId, 1)
+
+  /**
+   * Reject next read from storage operation for particular persistence id with `cause` exception.
+   */
+  def rejectNextRead(persistenceId: String, cause: Throwable): Unit = rejectNextNReads(persistenceId, 1, cause)
+
+  /**
+   * Reject next n read from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNReads(persistenceId: String, n: Int): Unit = rejectNextNReads(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n read from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.rejectNextNReads(persistenceId, n, cause)
+
+  /**
+   * Reject next delete from storage operation for any persistence id with default exception.
+   */
+  def rejectNextDelete(): Unit = rejectNextNDeletes(1)
+
+  /**
+   * Reject next delete from storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextDelete(cause: Throwable): Unit = rejectNextNDeletes(1, cause)
+
+  /**
+   * Reject next n delete from storage operations for any persistence id with default exception.
+   */
+  def rejectNextNDeletes(n: Int): Unit = rejectNextNDeletes(n, ExpectedRejection)
+
+  /**
+   * Reject next n delete from storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNDeletes(n: Int, cause: Throwable): Unit = scalaTestkit.rejectNextNDeletes(n, cause)
+
+  /**
+   * Reject next delete from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextDelete(persistenceId: String): Unit = rejectNextNDeletes(persistenceId, 1)
+
+  /**
+   * Reject next delete from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextDelete(persistenceId: String, cause: Throwable): Unit = rejectNextNDeletes(persistenceId, 1, cause)
+
+  /**
+   * Reject next n delete from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNDeletes(persistenceId: String, n: Int): Unit = rejectNextNDeletes(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n delete from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.rejectNextNDeletes(persistenceId, n, cause)
+
+  /**
+   * Reject `n` following journal operations depending on the condition `cond`.
+   * Rejection triggers, when `cond` returns true.
+   * Reject operations with default `ExpectedRejection` exception.
+   */
+  def rejectNextNOpsCond(cond: jf.BiFunction[String, JournalOperation, Boolean], n: Int): Unit =
+    rejectNextNOpsCond(cond, n, ExpectedRejection)
+
+  /**
+   * Reject `n` following journal operations depending on the condition `cond`.
+   * Rejection triggers, when `cond` returns true.
+   * Rejects operations with the `cause` exception.
+   */
+  def rejectNextNOpsCond(cond: jf.BiFunction[String, JournalOperation, Boolean], n: Int, cause: Throwable): Unit =
+    scalaTestkit.rejectNextNOpsCond((l: String, r: JournalOperation) => cond.apply(l, r), n, cause)
+
+  /**
+   * Reject n following journal operations regardless of their type.
+   * Rejects operations with default `ExpectedRejection` exception.
+   */
+  def rejectNextNOps(n: Int): Unit = rejectNextNOps(n, ExpectedRejection)
+
+  /**
+   * Reject `n` following journal operations regardless of their type.
+   * Rejects operations with the `cause` exception.
+   */
+  def rejectNextNOps(n: Int, cause: Throwable): Unit = scalaTestkit.rejectNextNOps(n, cause)
+
+  /**
+   * Persist `events` into storage in order.
+   */
+  def persistForRecovery(persistenceId: String, events: JList[Any]): Unit =
+    scalaTestkit.persistForRecovery(persistenceId, events.asScala.toVector)
+
+  /**
+   * Retrieve all events saved in storage by persistence id.
+   */
+  def persistedInStorage(persistenceId: String): JList[Any] = scalaTestkit.persistedInStorage(persistenceId).asJava
+
+  /**
+   * Clear all data from storage.
+   *
+   * NOTE! Also clears sequence numbers in storage!
+   *
+   * @see [[PersistenceTestKit.clearAllPreservingSeqNumbers()]]
+   */
+  def clearAll(): Unit = scalaTestkit.clearAll()
+
+  /**
+   * Clear all data from storage for particular persistence id.
+   *
+   * NOTE! Also clears sequence number in storage!
+   *
+   * @see [[PersistenceTestKit.clearByIdPreservingSeqNumbers()]]
+   */
+  def clearByPersistenceId(persistenceId: String): Unit = scalaTestkit.clearByPersistenceId(persistenceId)
+
+  /**
+   * Clear all data in storage preserving sequence numbers.
+   *
+   * @see [[PersistenceTestKit.clearAll()]]
+   */
+  def clearAllPreservingSeqNumbers(): Unit = scalaTestkit.clearAllPreservingSeqNumbers()
+
+  /**
+   * Clear all data in storage for particular persistence id preserving sequence numbers.
+   *
+   * @see [[PersistenceTestKit.clearByPersistenceId()]]
+   */
+  def clearByIdPreservingSeqNumbers(persistenceId: String): Unit =
+    scalaTestkit.clearByIdPreservingSeqNumbers(persistenceId)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOpsCond(cond: jf.BiFunction[String, JournalOperation, Boolean], n: Int): Unit =
+    failNextNOpsCond(cond, n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOpsCond(cond: jf.BiFunction[String, JournalOperation, Boolean], n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNOpsCond((l: String, r: JournalOperation) => cond.apply(l, r), n, cause)
+
+  /**
+   * Fail n following journal operations regardless of their type.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOps(n: Int): Unit =
+    failNextNOps(n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOps(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNOps(n, cause)
+
+  /**
+   * Set new processing policy for journal operations.
+   * NOTE! Overrides previously invoked `failNext...` or `rejectNext...`
+   */
+  def withPolicy(policy: EventStorage.JournalPolicies.PolicyType): PersistenceTestKit = {
+    scalaTestkit.withPolicy(policy)
+    this
+  }
+
+  /**
+   * Returns default policy if it was changed by [[PersistenceTestKit.withPolicy()]].
+   */
+  def returnDefaultPolicy(): Unit = scalaTestkit.returnDefaultPolicy()
+
+}
+
+object PersistenceTestKit {
+
+  import akka.actor.typed.{ ActorSystem => TypedActorSystem }
+
+  def create(system: ActorSystem): PersistenceTestKit = new PersistenceTestKit(system)
+
+  def create(system: TypedActorSystem[_]): PersistenceTestKit = create(system.classicSystem)
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/javadsl/SnapshotTestKit.scala

@@ -0,0 +1,273 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.ActorSystem
+import akka.persistence.testkit.scaladsl.{ SnapshotTestKit => ScalaTestKit }
+import akka.persistence.testkit.{ ExpectedFailure, SnapshotMeta, SnapshotOperation, SnapshotStorage }
+import akka.util.JavaDurationConverters._
+import akka.util.ccompat.JavaConverters._
+import java.time.Duration
+import java.util.{ List => JList }
+import java.util.{ function => jf }
+
+import akka.annotation.ApiMayChange
+import akka.japi.Pair
+
+/**
+ * Class for testing persisted snapshots in persistent actors.
+ */
+@ApiMayChange
+class SnapshotTestKit(system: ActorSystem) {
+
+  private val scalaTestkit = new ScalaTestKit(system)
+
+  /**
+   * Check that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String): Unit = scalaTestkit.expectNothingPersisted(persistenceId)
+
+  /**
+   * Check for `max` time that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String, max: Duration): Unit =
+    scalaTestkit.expectNothingPersisted(persistenceId, max.asScala)
+
+  /**
+   * Check that `snapshot` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, snapshot: A): A =
+    scalaTestkit.expectNextPersisted(persistenceId, snapshot)
+
+  /**
+   * Check for `max` time that `snapshot` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, snapshot: A, max: Duration): A =
+    scalaTestkit.expectNextPersisted(persistenceId, snapshot, max.asScala)
+
+  /**
+   * Check that next persisted in storage for particular persistence id snapshot has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A]): A =
+    scalaTestkit.expectNextPersistedClass[A](persistenceId, cla)
+
+  /**
+   * Check for `max` time that next persisted in storage for particular persistence id snapshot has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A], max: Duration): A =
+    scalaTestkit.expectNextPersistedClass[A](persistenceId, cla, max.asScala)
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNPersisted(persistenceId, n, cause)
+
+  /**
+   * Fail next `n` write operations for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int): Unit = failNextNPersisted(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNPersisted(n, cause)
+
+  /**
+   * Fail next `n` write operations with default exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int): Unit = failNextNPersisted(n, ExpectedFailure)
+
+  /**
+   * Fail next write operations with `cause` exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String, cause: Throwable): Unit = failNextNPersisted(persistenceId, 1, cause)
+
+  /**
+   * Fail next write operations with default exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String): Unit = failNextNPersisted(persistenceId, 1)
+
+  /**
+   * Fail next write operations with `cause` exception for any persistence id.
+   */
+  def failNextPersisted(cause: Throwable): Unit = failNextNPersisted(1, cause)
+
+  /**
+   * Fail next write operations with default exception for any persistence id.
+   */
+  def failNextPersisted(): Unit = failNextNPersisted(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for any persistence id.
+   */
+  def failNextRead(cause: Throwable): Unit = failNextNReads(1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(): Unit = failNextNReads(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for particular persistence id.
+   */
+  def failNextRead(persistenceId: String, cause: Throwable): Unit = failNextNReads(persistenceId, 1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(persistenceId: String): Unit = failNextNReads(persistenceId, 1)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for any persistence id.
+   */
+  def failNextNReads(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNReads(n, cause)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for any persistence id.
+   */
+  def failNextNReads(n: Int): Unit = failNextNReads(n, ExpectedFailure)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNReads(persistenceId, n, cause)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int): Unit = failNextNReads(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for any persistence id.
+   */
+  def failNextDelete(cause: Throwable): Unit = failNextNDeletes(1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for any persistence id.
+   */
+  def failNextDelete(): Unit = failNextNDeletes(1)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String, cause: Throwable): Unit = failNextNDeletes(persistenceId, 1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String): Unit = failNextNDeletes(persistenceId, 1)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNDeletes(n, cause)
+
+  /**
+   * Fail next n delete from storage attempts with default exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int): Unit = failNextNDeletes(n, ExpectedFailure)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNDeletes(persistenceId, n, cause)
+
+  /**
+   * Fail next n delete from storage attempts with default exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int): Unit = failNextNDeletes(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Receive next `n` snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A]): JList[A] =
+    scalaTestkit.receivePersisted[A](persistenceId, n, cla).asJava
+
+  /**
+   * Receive for `max` time next `n` snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A], max: Duration): JList[A] =
+    scalaTestkit.receivePersisted[A](persistenceId, n, cla, max.asScala).asJava
+
+  /**
+   * Persist `snapshots` with metadata into storage in order.
+   */
+  def persistForRecovery(persistenceId: String, snapshots: JList[Pair[SnapshotMeta, Any]]): Unit =
+    scalaTestkit.persistForRecovery(persistenceId, snapshots.asScala.toVector.map(_.toScala))
+
+  /**
+   * Retrieve all snapshots and their metadata saved in storage by persistence id.
+   */
+  def persistedInStorage(persistenceId: String): JList[Pair[SnapshotMeta, Any]] =
+    scalaTestkit.persistedInStorage(persistenceId).map(p => Pair(p._1, p._2)).asJava
+
+  /**
+   * Clear all data from storage.
+   */
+  def clearAll(): Unit = scalaTestkit.clearAll()
+
+  /**
+   * Clear all data from storage for particular persistence id.
+   */
+  def clearByPersistenceId(persistenceId: String): Unit = scalaTestkit.clearByPersistenceId(persistenceId)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOpsCond(cond: jf.BiFunction[String, SnapshotOperation, Boolean], n: Int): Unit =
+    failNextNOpsCond(cond, n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOpsCond(cond: jf.BiFunction[String, SnapshotOperation, Boolean], n: Int, cause: Throwable): Unit =
+    scalaTestkit.failNextNOpsCond((l: String, r: SnapshotOperation) => cond.apply(l, r), n, cause)
+
+  /**
+   * Fail n following journal operations regardless of their type.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOps(n: Int): Unit =
+    failNextNOps(n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOps(n: Int, cause: Throwable): Unit = scalaTestkit.failNextNOps(n, cause)
+
+  /**
+   * Set new processing policy for journal operations.
+   * NOTE! Overrides previously invoked `failNext...` or `rejectNext...`
+   */
+  def withPolicy(policy: SnapshotStorage.SnapshotPolicies.PolicyType): SnapshotTestKit = {
+    scalaTestkit.withPolicy(policy)
+    this
+  }
+
+  /**
+   * Returns default policy if it was changed by [[SnapshotTestKit.withPolicy()]].
+   */
+  def returnDefaultPolicy(): Unit = scalaTestkit.returnDefaultPolicy()
+
+}
+
+object SnapshotTestKit {
+
+  import akka.actor.typed.{ ActorSystem => TypedActorSystem }
+
+  def create(system: ActorSystem): SnapshotTestKit = new SnapshotTestKit(system)
+
+  def create(system: TypedActorSystem[_]): SnapshotTestKit = create(system.classicSystem)
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/scaladsl/PersistenceTestKit.scala

@@ -0,0 +1,521 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.{ ActorSystem, ExtendedActorSystem, Extension, ExtensionId }
+import akka.actor.typed.{ ActorSystem => TypedActorSystem }
+import akka.annotation.ApiMayChange
+import akka.persistence.testkit._
+import akka.persistence.testkit.internal.{ InMemStorageExtension, SnapshotStorageEmulatorExtension }
+import akka.persistence.{ Persistence, PersistentRepr, SnapshotMetadata }
+import akka.testkit.TestProbe
+import com.typesafe.config.Config
+
+import scala.collection.immutable
+import scala.concurrent.duration.FiniteDuration
+import scala.util.Try
+
+private[testkit] trait CommonTestKitOps[S, P] extends ClearOps with PolicyOpsTestKit[P] {
+  this: HasStorage[P, S] =>
+
+  /**
+   * Check that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String): Unit
+
+  /**
+   * Check for `max` time that nothing has been saved in the storage.
+   */
+  def expectNothingPersisted(persistenceId: String, max: FiniteDuration): Unit
+
+  /**
+   * Check that `event` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A): A
+
+  /**
+   * Check for `max` time that `event` has been saved in the storage.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A, max: FiniteDuration): A
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next `n` write operations for particular persistence id.
+   */
+  def failNextNPersisted(persistenceId: String, n: Int): Unit = failNextNPersisted(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next `n` write operations with the `cause` exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next `n` write operations with default exception for any persistence id.
+   */
+  def failNextNPersisted(n: Int): Unit = failNextNPersisted(n, ExpectedFailure)
+
+  /**
+   * Fail next write operation with `cause` exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String, cause: Throwable): Unit = failNextNPersisted(persistenceId, 1, cause)
+
+  /**
+   * Fail next write operation with default exception for particular persistence id.
+   */
+  def failNextPersisted(persistenceId: String): Unit = failNextNPersisted(persistenceId, 1)
+
+  /**
+   * Fail next write operation with `cause` exception for any persistence id.
+   */
+  def failNextPersisted(cause: Throwable): Unit = failNextNPersisted(1, cause)
+
+  /**
+   * Fail next write operation with default exception for any persistence id.
+   */
+  def failNextPersisted(): Unit = failNextNPersisted(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for any persistence id.
+   */
+  def failNextRead(cause: Throwable): Unit = failNextNReads(1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(): Unit = failNextNReads(1)
+
+  /**
+   * Fail next read from storage (recovery) attempt with `cause` exception for particular persistence id.
+   */
+  def failNextRead(persistenceId: String, cause: Throwable): Unit = failNextNReads(persistenceId, 1, cause)
+
+  /**
+   * Fail next read from storage (recovery) attempt with default exception for any persistence id.
+   */
+  def failNextRead(persistenceId: String): Unit = failNextNReads(persistenceId, 1)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for any persistence id.
+   */
+  def failNextNReads(n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for any persistence id.
+   */
+  def failNextNReads(n: Int): Unit = failNextNReads(n, ExpectedFailure)
+
+  /**
+   * Fail next n read from storage (recovery) attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next n read from storage (recovery) attempts with default exception for particular persistence id.
+   */
+  def failNextNReads(persistenceId: String, n: Int): Unit = failNextNReads(persistenceId, n, ExpectedFailure)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for any persistence id.
+   */
+  def failNextDelete(cause: Throwable): Unit = failNextNDeletes(1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for any persistence id.
+   */
+  def failNextDelete(): Unit = failNextNDeletes(1)
+
+  /**
+   * Fail next delete from storage attempt with `cause` exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String, cause: Throwable): Unit = failNextNDeletes(persistenceId, 1, cause)
+
+  /**
+   * Fail next delete from storage attempt with default exception for particular persistence id.
+   */
+  def failNextDelete(persistenceId: String): Unit = failNextNDeletes(persistenceId, 1)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next n delete from storage attempts with default exception for any persistence id.
+   */
+  def failNextNDeletes(n: Int): Unit = failNextNDeletes(n, ExpectedFailure)
+
+  /**
+   * Fail next n delete from storage attempts with `cause` exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Fail next n delete from storage attempts with default exception for particular persistence id.
+   */
+  def failNextNDeletes(persistenceId: String, n: Int): Unit = failNextNDeletes(persistenceId, n, ExpectedFailure)
+
+}
+
+private[testkit] trait PersistenceTestKitOps[S, P]
+    extends RejectSupport[P]
+    with ClearPreservingSeqNums
+    with CommonTestKitOps[S, P] {
+  this: HasStorage[P, S] =>
+
+  /**
+   * Reject next n save in storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Reject next n save in storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNPersisted(persistenceId: String, n: Int): Unit =
+    rejectNextNPersisted(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n save in storage operations for any persistence id with default exception.
+   */
+  def rejectNextNPersisted(n: Int): Unit = rejectNextNPersisted(n, ExpectedRejection)
+
+  /**
+   * Reject next n save in storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNPersisted(n: Int, cause: Throwable): Unit
+
+  /**
+   * Reject next save in storage operation for particular persistence id with default exception.
+   */
+  def rejectNextPersisted(persistenceId: String): Unit = rejectNextNPersisted(persistenceId, 1)
+
+  /**
+   * Reject next save in storage operation for particular persistence id with `cause` exception.
+   */
+  def rejectNextPersisted(persistenceId: String, cause: Throwable): Unit = rejectNextNPersisted(persistenceId, 1, cause)
+
+  /**
+   * Reject next save in storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextPersisted(cause: Throwable): Unit = rejectNextNPersisted(1, cause)
+
+  /**
+   * Reject next save in storage operation for any persistence id with default exception.
+   */
+  def rejectNextPersisted(): Unit = rejectNextNPersisted(1)
+
+  /**
+   * Reject next read from storage operation for any persistence id with default exception.
+   */
+  def rejectNextRead(): Unit = rejectNextNReads(1)
+
+  /**
+   * Reject next read from storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextRead(cause: Throwable): Unit = rejectNextNReads(1, cause)
+
+  /**
+   * Reject next n read from storage operations for any persistence id with default exception.
+   */
+  def rejectNextNReads(n: Int): Unit = rejectNextNReads(n, ExpectedRejection)
+
+  /**
+   * Reject next n read from storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNReads(n: Int, cause: Throwable): Unit
+
+  /**
+   * Reject next read from storage operation for particular persistence id with default exception.
+   */
+  def rejectNextRead(persistenceId: String): Unit = rejectNextNReads(persistenceId, 1)
+
+  /**
+   * Reject next read from storage operation for particular persistence id with `cause` exception.
+   */
+  def rejectNextRead(persistenceId: String, cause: Throwable): Unit = rejectNextNReads(persistenceId, 1, cause)
+
+  /**
+   * Reject next n read from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNReads(persistenceId: String, n: Int): Unit = rejectNextNReads(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n read from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Reject next delete from storage operation for any persistence id with default exception.
+   */
+  def rejectNextDelete(): Unit = rejectNextNDeletes(1)
+
+  /**
+   * Reject next delete from storage operation for any persistence id with `cause` exception.
+   */
+  def rejectNextDelete(cause: Throwable): Unit = rejectNextNDeletes(1, cause)
+
+  /**
+   * Reject next n delete from storage operations for any persistence id with default exception.
+   */
+  def rejectNextNDeletes(n: Int): Unit = rejectNextNDeletes(n, ExpectedRejection)
+
+  /**
+   * Reject next n delete from storage operations for any persistence id with `cause` exception.
+   */
+  def rejectNextNDeletes(n: Int, cause: Throwable): Unit
+
+  /**
+   * Reject next delete from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextDelete(persistenceId: String): Unit = rejectNextNDeletes(persistenceId, 1)
+
+  /**
+   * Reject next delete from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextDelete(persistenceId: String, cause: Throwable): Unit = rejectNextNDeletes(persistenceId, 1, cause)
+
+  /**
+   * Reject next n delete from storage operations for particular persistence id with default exception.
+   */
+  def rejectNextNDeletes(persistenceId: String, n: Int): Unit = rejectNextNDeletes(persistenceId, n, ExpectedRejection)
+
+  /**
+   * Reject next n delete from storage operations for particular persistence id with `cause` exception.
+   */
+  def rejectNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit
+
+  /**
+   * Persist `snapshots` into storage in order.
+   */
+  def persistForRecovery(persistenceId: String, snapshots: immutable.Seq[Any]): Unit
+
+  /**
+   * Retrieve all snapshots saved in storage by persistence id.
+   */
+  def persistedInStorage(persistenceId: String): immutable.Seq[Any]
+
+}
+
+/**
+ * Class for testing snapshots of persistent actors.
+ *
+ * NOTE! ActorSystem must be configured with [[PersistenceTestKitSnapshotPlugin]].
+ * The configuration can be retrieved with [[PersistenceTestKitSnapshotPlugin.config]].
+ */
+@ApiMayChange
+class SnapshotTestKit(system: ActorSystem)
+    extends CommonTestKitOps[(SnapshotMetadata, Any), SnapshotOperation]
+    with PolicyOpsTestKit[SnapshotOperation]
+    with ExpectOps[(SnapshotMetadata, Any)]
+    with HasStorage[SnapshotOperation, (SnapshotMetadata, Any)] {
+  require(
+    Try(Persistence(system).journalFor(PersistenceTestKitSnapshotPlugin.PluginId)).isSuccess,
+    "The test persistence plugin for snapshots is not configured.")
+
+  import SnapshotTestKit._
+
+  override protected val storage: SnapshotStorage = SnapshotStorageEmulatorExtension(system)
+
+  private val settings = Settings(system)
+
+  override private[testkit] val probe = TestProbe()(system)
+
+  override private[testkit] val pollInterval: FiniteDuration = settings.pollInterval
+
+  override private[testkit] val maxTimeout: FiniteDuration = settings.assertTimeout
+
+  override private[testkit] val Policies = SnapshotStorage.SnapshotPolicies
+
+  override def failNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[WriteSnapshot], n, cause)
+
+  override def failNextNPersisted(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[WriteSnapshot], n, cause)
+
+  override def failNextNReads(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[ReadSnapshot], n, cause)
+
+  override def failNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[ReadSnapshot], n, cause)
+
+  override def failNextNDeletes(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[DeleteSnapshot], n, cause)
+
+  override def failNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[DeleteSnapshot], n, cause)
+
+  /**
+   * Persist `elems` pairs of (snapshot metadata, snapshot payload) into storage.
+   */
+  def persistForRecovery(persistenceId: String, elems: immutable.Seq[(SnapshotMeta, Any)]): Unit =
+    elems.foreach {
+      case (m, p) =>
+        storage.add(persistenceId, (SnapshotMetadata(persistenceId, m.sequenceNr, m.timestamp), p))
+        addToIndex(persistenceId, 1)
+    }
+
+  /**
+   * Persist a pair of (snapshot metadata, snapshot payload) into storage.
+   */
+  def persistForRecovery(persistenceId: String, elem: (SnapshotMeta, Any)): Unit =
+    persistForRecovery(persistenceId, immutable.Seq(elem))
+
+  /**
+   * Retrieve snapshots and their metadata from storage by persistence id.
+   */
+  def persistedInStorage(persistenceId: String): immutable.Seq[(SnapshotMeta, Any)] =
+    storage
+      .read(persistenceId)
+      .map(_.map(m => (SnapshotMeta(m._1.sequenceNr, m._1.timestamp), m._2)))
+      .getOrElse(Vector.empty)
+
+  override private[testkit] def reprToAny(repr: (SnapshotMetadata, Any)) = repr._2
+
+}
+
+@ApiMayChange
+object SnapshotTestKit {
+
+  def apply(implicit system: ActorSystem): SnapshotTestKit = new SnapshotTestKit(system)
+
+  def apply(implicit system: TypedActorSystem[_]): SnapshotTestKit = apply(system.classicSystem)
+
+  object Settings extends ExtensionId[Settings] {
+
+    val configPath = "akka.persistence.testkit.snapshots"
+
+    override def createExtension(system: ExtendedActorSystem): Settings =
+      new Settings(system.settings.config.getConfig(configPath))
+
+    override def get(system: ActorSystem): Settings = super.get(system)
+
+  }
+
+  class Settings(config: Config) extends Extension {
+
+    import akka.util.Helpers._
+
+    val serialize: Boolean = config.getBoolean("serialize")
+    val assertTimeout: FiniteDuration = config.getMillisDuration("assert-timeout")
+    val pollInterval: FiniteDuration = config.getMillisDuration("assert-poll-interval")
+
+  }
+
+}
+
+/**
+ * Class for testing events of persistent actors.
+ *
+ * NOTE! ActorSystem must be configured with [[PersistenceTestKitPlugin]].
+ * The configuration can be retrieved with [[PersistenceTestKitPlugin.config]].
+ */
+@ApiMayChange
+class PersistenceTestKit(system: ActorSystem)
+    extends PersistenceTestKitOps[PersistentRepr, JournalOperation]
+    with ExpectOps[PersistentRepr]
+    with HasStorage[JournalOperation, PersistentRepr] {
+  require(
+    Try(Persistence(system).journalFor(PersistenceTestKitPlugin.PluginId)).isSuccess,
+    "The test persistence plugin is not configured.")
+
+  import PersistenceTestKit._
+
+  override protected val storage = InMemStorageExtension(system)
+
+  private final lazy val settings = Settings(system)
+
+  override private[testkit] val probe = TestProbe()(system)
+
+  override private[testkit] val Policies = EventStorage.JournalPolicies
+
+  override private[testkit] val pollInterval: FiniteDuration = settings.pollInterval
+
+  override private[testkit] val maxTimeout: FiniteDuration = settings.assertTimeout
+
+  override def rejectNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[WriteEvents], n, cause)
+
+  override def rejectNextNPersisted(n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond((_, op) => op.isInstanceOf[WriteEvents], n, cause)
+
+  override def rejectNextNReads(n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond((_, op) => op.isInstanceOf[ReadEvents] || op.isInstanceOf[ReadSeqNum.type], n, cause)
+
+  override def rejectNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond(
+      (pid, op) => (pid == persistenceId) && (op.isInstanceOf[ReadEvents] || op.isInstanceOf[ReadSeqNum.type]),
+      n,
+      cause)
+
+  override def rejectNextNDeletes(n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond((_, op) => op.isInstanceOf[DeleteEvents], n, cause)
+
+  override def rejectNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    rejectNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[DeleteEvents], n, cause)
+
+  override def failNextNPersisted(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[WriteEvents], n, cause)
+
+  override def failNextNPersisted(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[WriteEvents], n, cause)
+
+  override def failNextNReads(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[ReadEvents] || op.isInstanceOf[ReadSeqNum.type], n, cause)
+
+  override def failNextNReads(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond(
+      (pid, op) => (pid == persistenceId) && (op.isInstanceOf[ReadEvents] || op.isInstanceOf[ReadSeqNum.type]),
+      n,
+      cause)
+
+  override def failNextNDeletes(n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((_, op) => op.isInstanceOf[DeleteEvents], n, cause)
+
+  override def failNextNDeletes(persistenceId: String, n: Int, cause: Throwable): Unit =
+    failNextNOpsCond((pid, op) => pid == persistenceId && op.isInstanceOf[DeleteEvents], n, cause)
+
+  def persistForRecovery(persistenceId: String, snapshots: immutable.Seq[Any]): Unit = {
+    storage.addAny(persistenceId, snapshots)
+    addToIndex(persistenceId, snapshots.size)
+  }
+
+  def persistedInStorage(persistenceId: String): immutable.Seq[Any] =
+    storage.read(persistenceId).getOrElse(List.empty).map(reprToAny)
+
+  override private[testkit] def reprToAny(repr: PersistentRepr): Any = repr.payload
+}
+
+@ApiMayChange
+object PersistenceTestKit {
+
+  def apply(system: ActorSystem): PersistenceTestKit = new PersistenceTestKit(system)
+
+  def apply(system: TypedActorSystem[_]): PersistenceTestKit = apply(system.classicSystem)
+
+  object Settings extends ExtensionId[Settings] {
+
+    val configPath = "akka.persistence.testkit.events"
+
+    override def get(system: ActorSystem): Settings = super.get(system)
+
+    override def createExtension(system: ExtendedActorSystem): Settings =
+      new Settings(system.settings.config.getConfig(configPath))
+
+  }
+
+  class Settings(config: Config) extends Extension {
+
+    import akka.util.Helpers._
+
+    val serialize: Boolean = config.getBoolean("serialize")
+    val assertTimeout: FiniteDuration = config.getMillisDuration("assert-timeout")
+    val pollInterval: FiniteDuration = config.getMillisDuration("assert-poll-interval")
+
+  }
+
+}

akka-persistence-testkit/src/main/scala/akka/persistence/testkit/scaladsl/TestOps.scala

@@ -0,0 +1,336 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.persistence.testkit.ProcessingPolicy.DefaultPolicies
+import akka.persistence.testkit.internal.TestKitStorage
+import akka.persistence.testkit.{ ExpectedFailure, ExpectedRejection }
+import akka.testkit.TestKitBase
+import akka.util
+import akka.util.BoxedType
+
+import scala.collection.immutable
+import scala.concurrent.duration.FiniteDuration
+import scala.reflect.ClassTag
+
+private[testkit] trait RejectSupport[U] {
+  this: PolicyOpsTestKit[U] with HasStorage[U, _] =>
+
+  /**
+   * Reject `n` following journal operations depending on the condition `cond`.
+   * Rejection triggers, when `cond` returns true.
+   * Reject operations with default `ExpectedRejection` exception.
+   */
+  def rejectNextNOpsCond(cond: (String, U) => Boolean, n: Int): Unit =
+    rejectNextNOpsCond(cond, n, ExpectedRejection)
+
+  /**
+   * Reject `n` following journal operations depending on the condition `cond`.
+   * Rejection triggers, when `cond` returns true.
+   * Rejects operations with the `cause` exception.
+   */
+  def rejectNextNOpsCond(cond: (String, U) => Boolean, n: Int, cause: Throwable): Unit = {
+    val current = storage.currentPolicy
+    val pol = new Policies.RejectNextNCond(n, cause, cond, withPolicy(current))
+    withPolicy(pol)
+  }
+
+  /**
+   * Reject n following journal operations regardless of their type.
+   * Rejects operations with default `ExpectedRejection` exception.
+   */
+  def rejectNextNOps(n: Int): Unit =
+    rejectNextNOps(n, ExpectedRejection)
+
+  /**
+   * Reject `n` following journal operations regardless of their type.
+   * Rejects operations with the `cause` exception.
+   */
+  def rejectNextNOps(n: Int, cause: Throwable): Unit = {
+    val current = storage.currentPolicy
+    val pol = new Policies.RejectNextN(n, cause, withPolicy(current))
+    withPolicy(pol)
+  }
+
+}
+
+private[testkit] trait PolicyOpsTestKit[P] extends {
+  this: HasStorage[P, _] =>
+
+  private[testkit] val Policies: DefaultPolicies[P]
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOpsCond(cond: (String, P) => Boolean, n: Int): Unit =
+    failNextNOpsCond(cond, n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations depending on the condition `cond`.
+   * Failure triggers, when `cond` returns true.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOpsCond(cond: (String, P) => Boolean, n: Int, cause: Throwable): Unit = {
+    val current = storage.currentPolicy
+    val pol = new Policies.FailNextNCond(n, cause, cond, withPolicy(current))
+    withPolicy(pol)
+  }
+
+  /**
+   * Fail n following journal operations regardless of their type.
+   * Fails operations with default `ExpectedFailure` exception.
+   */
+  def failNextNOps(n: Int): Unit =
+    failNextNOps(n, ExpectedFailure)
+
+  /**
+   * Fail `n` following journal operations regardless of their type.
+   * Fails operations with the `cause` exception.
+   */
+  def failNextNOps(n: Int, cause: Throwable): Unit = {
+    val current = storage.currentPolicy
+    val pol = new Policies.FailNextN(n, cause, withPolicy(current))
+    withPolicy(pol)
+  }
+
+  /**
+   * Set new processing policy for journal operations.
+   * NOTE! Overrides previously invoked `failNext...` or `rejectNext...`
+   */
+  def withPolicy(policy: Policies.PolicyType): this.type = {
+    storage.setPolicy(policy)
+    this
+  }
+
+  /**
+   * Returns default policy if it was changed by [[PolicyOpsTestKit.this.withPolicy()]].
+   */
+  def returnDefaultPolicy(): Unit = storage.returnDefaultPolicy()
+
+}
+
+private[testkit] trait ExpectOps[U] {
+  this: HasStorage[_, U] =>
+
+  private[testkit] val probe: TestKitBase
+
+  import probe._
+  import akka.testkit._
+
+  private[testkit] def pollInterval: FiniteDuration
+
+  private[testkit] def maxTimeout: FiniteDuration
+
+  private[testkit] def reprToAny(repr: U): Any
+
+  /**
+   * Check that next persisted in storage for particular persistence id event/snapshot was `event`.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A): A =
+    expectNextPersisted(persistenceId, event, maxTimeout)
+
+  /**
+   * Check for `max` time that next persisted in storage for particular persistence id event/snapshot was `event`.
+   */
+  def expectNextPersisted[A](persistenceId: String, event: A, max: FiniteDuration): A = {
+    val nextInd = nextIndex(persistenceId)
+    val expected = Some(event)
+    val res = awaitAssert({
+      val actual = storage.findOneByIndex(persistenceId, nextInd).map(reprToAny)
+      assert(actual == expected, s"Failed to persist $event, got $actual instead")
+      actual
+    }, max = max.dilated, interval = pollInterval)
+
+    setIndex(persistenceId, nextInd + 1)
+    res.get.asInstanceOf[A]
+  }
+
+  /**
+   * Check that next persisted in storage for particular persistence id event/snapshot has expected type.
+   */
+  def expectNextPersistedType[A](persistenceId: String)(implicit t: ClassTag[A]): A =
+    expectNextPersistedType(persistenceId, maxTimeout)
+
+  /**
+   * Check for `max` time that next persisted in storage for particular persistence id event/snapshot has expected type.
+   */
+  def expectNextPersistedType[A](persistenceId: String, max: FiniteDuration)(implicit t: ClassTag[A]): A =
+    expectNextPersistedClass(persistenceId, t.runtimeClass.asInstanceOf[Class[A]], max)
+
+  /**
+   * Check that next persisted in storage for particular persistence id event/snapshot has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A]): A =
+    expectNextPersistedClass(persistenceId, cla, maxTimeout)
+
+  /**
+   * Check for `max` time that next persisted in storage for particular persistence id event/snapshot has expected type.
+   */
+  def expectNextPersistedClass[A](persistenceId: String, cla: Class[A], max: FiniteDuration): A = {
+    val nextInd = nextIndex(persistenceId)
+    val c = util.BoxedType(cla)
+    val res = awaitAssert({
+      val actual = storage.findOneByIndex(persistenceId, nextInd).map(reprToAny)
+      assert(actual.isDefined, s"Expected: $cla but got no event")
+      val a = actual.get
+      assert(c.isInstance(a), s"Expected: $cla but got unexpected ${a.getClass}")
+      a.asInstanceOf[A]
+    }, max.dilated, interval = pollInterval)
+    setIndex(persistenceId, nextInd + 1)
+    res
+  }
+
+  /**
+   * Check that nothing was persisted in storage for particular persistence id.
+   */
+  def expectNothingPersisted(persistenceId: String): Unit =
+    expectNothingPersisted(persistenceId, maxTimeout)
+
+  /**
+   * Check for `max` time that nothing was persisted in storage for particular persistence id.
+   */
+  def expectNothingPersisted(persistenceId: String, max: FiniteDuration): Unit = {
+    val nextInd = nextIndex(persistenceId)
+    assertForDuration({
+      val actual = storage.findOneByIndex(persistenceId, nextInd).map(reprToAny)
+      val res = actual.isEmpty
+      assert(res, s"Found persisted event $actual, but expected None instead")
+    }, max = max.dilated, interval = pollInterval)
+  }
+
+  /**
+   * Receive for `max` time next `n` events/snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, max: FiniteDuration)(
+      implicit t: ClassTag[A]): immutable.Seq[A] =
+    receivePersisted(persistenceId, n, t.runtimeClass.asInstanceOf[Class[A]], max)
+
+  /**
+   * Receive next `n` events/snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int)(implicit t: ClassTag[A]): immutable.Seq[A] =
+    receivePersisted(persistenceId, n, t.runtimeClass.asInstanceOf[Class[A]], maxTimeout)
+
+  /**
+   * Receive next `n` events/snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A]): immutable.Seq[A] =
+    receivePersisted(persistenceId, n, cla, maxTimeout)
+
+  /**
+   * Receive for `max` time next `n` events/snapshots that have been persisted in the storage.
+   */
+  def receivePersisted[A](persistenceId: String, n: Int, cla: Class[A], max: FiniteDuration): immutable.Seq[A] = {
+    val nextInd = nextIndex(persistenceId)
+    val bt = BoxedType(cla)
+    val res =
+      awaitAssert(
+        {
+          val actual = storage.findMany(persistenceId, nextInd, n)
+          actual match {
+            case Some(reprs) =>
+              val ls = reprs.map(reprToAny)
+              val filtered = ls.filter(e => !bt.isInstance(e))
+              assert(ls.size == n, s"Could read only ${ls.size} events instead of expected $n")
+              assert(filtered.isEmpty, s"Persisted events $filtered do not correspond to expected type")
+            case None => assert(false, "No events were persisted")
+          }
+          actual.get.map(reprToAny)
+        },
+        max = max.dilated,
+        interval = pollInterval)
+
+    setIndex(persistenceId, nextInd + n)
+    res.asInstanceOf[immutable.Seq[A]]
+  }
+
+}
+
+private[testkit] trait ClearOps {
+  this: HasStorage[_, _] =>
+
+  /**
+   * Clear all data from the storage.
+   *
+   * NOTE! Also clears sequence numbers in storage!
+   *
+   * @see [[ClearPreservingSeqNums.clearAllPreservingSeqNumbers()]]
+   */
+  def clearAll(): Unit = {
+    storage.clearAll()
+    clearIndexStorage()
+  }
+
+  /**
+   * Clear all data from the storage for particular persistence id.
+   *
+   * NOTE! Also clears sequence number in the storage!
+   *
+   * @see [[ClearPreservingSeqNums.clearByIdPreservingSeqNumbers()]]
+   */
+  def clearByPersistenceId(persistenceId: String): Unit = {
+    storage.removeKey(persistenceId)
+    removeLastIndex(persistenceId)
+  }
+
+}
+
+private[testkit] trait ClearPreservingSeqNums {
+  this: HasStorage[_, _] =>
+
+  /**
+   * Clear all data in the storage preserving sequence numbers.
+   *
+   * @see [[ClearOps.clearAll()]]
+   */
+  def clearAllPreservingSeqNumbers(): Unit = {
+    storage.clearAllPreservingSeqNumbers()
+    clearIndexStorage()
+  }
+
+  /**
+   * Clear all data in the storage for particular persistence id preserving sequence numbers.
+   *
+   * @see [[ClearOps.clearByPersistenceId()]]
+   */
+  def clearByIdPreservingSeqNumbers(persistenceId: String): Unit = {
+    storage.removePreservingSeqNumber(persistenceId)
+    removeLastIndex(persistenceId)
+  }
+
+}
+
+/**
+ * Abstract persistent storage for tests.
+ * Has additional methods for keeping track of the indexes of last events persisted in the storage during test.
+ */
+private[testkit] trait HasStorage[P, R] {
+
+  protected def storage: TestKitStorage[P, R]
+
+  //todo needs to be thread safe (atomic read-increment-write) for parallel tests. Do we need parallel tests support?
+  @volatile
+  private var nextIndexByPersistenceId: immutable.Map[String, Int] = Map.empty
+
+  private[testkit] def removeLastIndex(persistenceId: String): Unit =
+    nextIndexByPersistenceId -= persistenceId
+
+  private[testkit] def clearIndexStorage(): Unit =
+    nextIndexByPersistenceId = Map.empty
+
+  private[testkit] def nextIndex(persistenceId: String): Int =
+    nextIndexByPersistenceId.getOrElse(persistenceId, 0)
+
+  private[testkit] def setIndex(persistenceId: String, index: Int): Unit =
+    nextIndexByPersistenceId += persistenceId -> index
+
+  private[testkit] def addToIndex(persistenceId: String, add: Int): Unit = {
+    val nextInd = nextIndexByPersistenceId.getOrElse(persistenceId, 0)
+    nextIndexByPersistenceId += (persistenceId -> (nextInd + add))
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/CommonUtils.scala

@@ -0,0 +1,105 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit
+
+import java.util.UUID
+
+import akka.actor.{ ActorRef, ActorSystem }
+import akka.persistence._
+import akka.testkit.TestKitBase
+import com.typesafe.config.ConfigFactory
+import org.scalatest.wordspec.AnyWordSpecLike
+
+trait CommonUtils extends AnyWordSpecLike with TestKitBase {
+
+  protected def randomPid() = UUID.randomUUID().toString
+
+  import akka.util.ccompat.JavaConverters._
+
+  def initSystemWithEnabledPlugin(name: String, serializeMessages: Boolean, serializeSnapshots: Boolean) =
+    ActorSystem(
+      s"persistence-testkit-$name",
+      PersistenceTestKitSnapshotPlugin.config
+        .withFallback(PersistenceTestKitPlugin.config)
+        .withFallback(
+          ConfigFactory.parseMap(
+            Map(
+              // testing serialization of the events when persisting in the storage
+              // using default java serializers for convenience
+              "akka.actor.allow-java-serialization" -> true,
+              "akka.persistence.testkit.events.serialize" -> serializeMessages,
+              "akka.persistence.testkit.snapshots.serialize" -> serializeSnapshots).asJava))
+        .withFallback(ConfigFactory.parseString("akka.loggers = [\"akka.testkit.TestEventListener\"]"))
+        .withFallback(ConfigFactory.defaultApplication()))
+
+}
+
+case class NewSnapshot(state: Any)
+case object DeleteAllMessages
+case class DeleteSomeSnapshot(seqNum: Long)
+case class DeleteSomeSnapshotByCriteria(crit: SnapshotSelectionCriteria)
+case object AskMessageSeqNum
+case object AskSnapshotSeqNum
+case class DeleteSomeMessages(upToSeqNum: Long)
+
+class C
+
+case class B(i: Int)
+
+class A(pid: String, notifyOnStateChange: Option[ActorRef]) extends PersistentActor {
+
+  import scala.collection.immutable
+
+  var recovered = immutable.List.empty[Any]
+  var snapshotState = 0
+
+  override def receiveRecover = {
+    case SnapshotOffer(_, snapshot: Int) =>
+      snapshotState = snapshot
+    case RecoveryCompleted =>
+      notifyOnStateChange.foreach(_ ! Tuple2(recovered, snapshotState))
+    case s => recovered :+= s
+  }
+
+  override def receiveCommand = {
+    case AskMessageSeqNum =>
+      notifyOnStateChange.foreach(_ ! lastSequenceNr)
+    case AskSnapshotSeqNum =>
+      notifyOnStateChange.foreach(_ ! snapshotSequenceNr)
+    case d @ DeleteMessagesFailure(_, _) =>
+      notifyOnStateChange.foreach(_ ! d)
+    case d @ DeleteMessagesSuccess(_) =>
+      notifyOnStateChange.foreach(_ ! d)
+    case s: SnapshotProtocol.Response =>
+      notifyOnStateChange.foreach(_ ! s)
+    case DeleteAllMessages =>
+      deleteMessages(lastSequenceNr)
+    case DeleteSomeSnapshot(sn) =>
+      deleteSnapshot(sn)
+    case DeleteSomeSnapshotByCriteria(crit) =>
+      deleteSnapshots(crit)
+    case DeleteSomeMessages(sn) =>
+      deleteMessages(sn)
+    case NewSnapshot(state: Int) =>
+      snapshotState = state: Int
+      saveSnapshot(state)
+    case NewSnapshot(other) =>
+      saveSnapshot(other)
+    case s =>
+      persist(s) { _ =>
+        sender() ! s
+      }
+  }
+
+  override def persistenceId = pid
+}
+
+trait TestCommand
+case class Cmd(data: String) extends TestCommand
+case object Passivate extends TestCommand
+case class Evt(data: String)
+case class EmptyState()
+case object Recovered
+case object Stopped

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/CommonSnapshotTests.scala

@@ -0,0 +1,523 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.Props
+import akka.persistence._
+import akka.persistence.testkit._
+import akka.testkit.EventFilter
+import org.scalatest.matchers.should.Matchers._
+import akka.util.ccompat.JavaConverters._
+import akka.japi.Pair
+import akka.actor.typed.javadsl.Adapter
+
+trait CommonSnapshotTests extends JavaDslUtils {
+
+  lazy val testKit = new SnapshotTestKit(system)
+  import testKit._
+
+  def specificTests(): Unit
+
+  "SnapshotTestKit" should {
+
+    "work with typed actors" in {
+      val pid = randomPid()
+      val act = Adapter.spawn(system, eventSourcedBehavior(pid), pid)
+      act ! Cmd("")
+      testKit.expectNextPersisted(pid, EmptyState())
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "save snapshot" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(1: Any)
+      a ! NewSnapshot(2: Any)
+
+      expectNextPersisted(pid, 1)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, 3)
+      }
+
+      expectNextPersisted(pid, 2)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, 3)
+      }
+
+    }
+
+    "successfully set and execute custom policy" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val newPolicy = new SnapshotStorage.SnapshotPolicies.PolicyType {
+        override def tryProcess(persistenceId: String, processingUnit: SnapshotOperation): ProcessingResult = {
+          processingUnit match {
+            case WriteSnapshot(_, msgs) =>
+              val ex = msgs match {
+                case 777 => true
+                case _   => false
+              }
+              if (ex) {
+                ProcessingSuccess
+              } else {
+                StorageFailure(err)
+              }
+            case _ => ProcessingSuccess
+          }
+        }
+      }
+
+      withPolicy(newPolicy)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ee) if ee.getMessage == err.getMessage => }
+
+      a ! NewSnapshot(777)
+
+      expectMsgPF() { case SaveSnapshotSuccess(_) => }
+      expectNextPersisted(pid, 777)
+
+      returnDefaultPolicy()
+
+    }
+
+    "expect next N valid snapshots in order" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(2)
+      a ! NewSnapshot(1)
+
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 3, classOf[Int])
+      }
+
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 2, classOf[String])
+      }
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 3, classOf[Int])
+      }
+      val li = receivePersisted(pid, 2, classOf[Int])
+      (li should contain).theSameElementsInOrderAs(List(2, 1))
+    }
+
+    "fail to receive" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(2)
+      a ! NewSnapshot("data")
+
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 3, classOf[Int])
+      }
+
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 2, classOf[String])
+      }
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 3, classOf[Int])
+      }
+      val li = receivePersisted(pid, 2, classOf[Any])
+      (li should contain).theSameElementsInOrderAs(List(2, "data"))
+    }
+
+    "fail next snapshot" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      //consecutive calls should stack
+      failNextPersisted()
+      failNextPersisted()
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ExpectedFailure) => }
+
+      val b = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      b ! NewSnapshot(2)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ExpectedFailure) => }
+
+      val c = system.actorOf(Props(classOf[A], pid, None))
+
+      c ! NewSnapshot(3)
+
+      expectNextPersisted(pid, 3)
+
+    }
+
+    "fail next snapshot with custom error" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val err = new Exception("Custom ERROR!")
+
+      failNextPersisted(err)
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ee) if err.getMessage == ee.getMessage => }
+
+    }
+
+    "expect nothingPersisted fails" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! NewSnapshot(1)
+
+      assertThrows[AssertionError] {
+        expectNothingPersisted(pid)
+      }
+
+    }
+
+    "expect no snapshot persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! NewSnapshot(1)
+
+      expectNextPersisted(pid, 1)
+
+      expectNothingPersisted(pid)
+
+    }
+
+    "fail recovery" in {
+
+      val pid = randomPid()
+
+      failNextNOps(1)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      watch(a)
+
+      expectTerminated(a)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+    }
+
+    "recover last persisted snapshot" in {
+
+      val pid = randomPid()
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      persistForRecovery(pid, preload)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    "fail to recover persisted snapshots for any actor" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      persistForRecovery(pid, preload)
+
+      failNextRead()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "fail to recover persisted snapshots for any actor with custom error" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      val err = new Exception("Custom ERROR!")
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+        watch(a)
+        expectTerminated(a)
+      }
+
+    }
+
+    "fail to recover persisted snapshots for actor with particular persistenceId" in {
+
+      val pid = randomPid()
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(pid)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "recover last persisted snapshot when fail for different persistenceId is set" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      persistForRecovery(pid, preload)
+
+      val otherPid = randomPid()
+
+      failNextRead(otherPid)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    "persist and return persisted snapshots" in {
+
+      val pid = randomPid()
+
+      val saved = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+        .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+        .asJava
+
+      persistForRecovery(pid, saved)
+
+      val li = persistedInStorage(pid).asScala
+
+      (li should contain).theSameElementsInOrderAs(saved.asScala)
+
+    }
+
+    "fail next snapshot delete for any actor" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1)).map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2)).asJava)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete()
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 1))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ExpectedFailure) => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "fail next snapshot delete for any actor with custom error" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1)).map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2)).asJava)
+
+      val err = new Exception("Custom ERROR!")
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(err)
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 1))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ee) if ee.getMessage == err.getMessage => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "fail next delete for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(
+        pid,
+        List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+          .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+          .asJava)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(pid)
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 3))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ExpectedFailure) => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "not fail next delete for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(
+        pid,
+        List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+          .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+          .asJava)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val other = randomPid()
+
+      failNextDelete(other)
+
+      a ! DeleteSomeSnapshotByCriteria(SnapshotSelectionCriteria.Latest)
+
+      expectMsg((List.empty, 3))
+      expectMsgPF() { case DeleteSnapshotsSuccess(SnapshotSelectionCriteria.Latest) => }
+
+    }
+
+    "clear all" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(
+        pid,
+        List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+          .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+          .asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearAll()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskSnapshotSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "clear all for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(
+        pid,
+        List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+          .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+          .asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearByPersistenceId(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskSnapshotSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "preserve all for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(
+        pid,
+        List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+          .map(tpl => Pair[SnapshotMeta, Any](tpl._1, tpl._2))
+          .asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearByPersistenceId(randomPid())
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    specificTests()
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/CommonTestKitTests.scala

@@ -0,0 +1,580 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.Props
+import akka.persistence._
+import akka.persistence.testkit._
+import akka.testkit.EventFilter
+import org.scalatest.matchers.should.Matchers._
+import akka.util.ccompat.JavaConverters._
+import akka.actor.typed.javadsl.Adapter
+
+trait CommonTestKitTests extends JavaDslUtils {
+
+  lazy val testKit = new PersistenceTestKit(system)
+  import testKit._
+
+  def specificTests(): Unit
+
+  "PersistenceTestKit" should {
+
+    "work with typed actors" in {
+      val expectedId = randomPid()
+      val pid = randomPid()
+      val act = Adapter.spawn(system, eventSourcedBehavior(pid), pid)
+      act ! Cmd(expectedId)
+
+      testKit.expectNextPersisted(pid, Evt(expectedId))
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "work with tagged events" in {
+      val expectedId = randomPid()
+      val pid = randomPid()
+      var act =
+        Adapter.spawn(system, eventSourcedBehavior(pid, true, Some(Adapter.toTyped[Any](testActor))), randomPid())
+      expectMsg(Recovered)
+      act ! Cmd(expectedId)
+      testKit.expectNextPersisted(pid, Evt(expectedId))
+      act ! Passivate
+      expectMsg(Stopped)
+
+      act = Adapter.spawn(system, eventSourcedBehavior(pid, true, Some(Adapter.toTyped[Any](testActor))), randomPid())
+      val expectedId2 = randomPid()
+      act ! Cmd(expectedId2)
+      expectMsg(Recovered)
+      testKit.expectNextPersisted(pid, Evt(expectedId2))
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "expect next valid message" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! B(1)
+      a ! B(2)
+
+      expectNextPersisted(pid, B(1))
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(3))
+      }
+
+      expectNextPersisted(pid, B(2))
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(3))
+      }
+
+    }
+
+    "expect next N valid messages in order" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! B(1)
+      a ! B(2)
+
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 3, classOf[B])
+      }
+      assertThrows[AssertionError] {
+        receivePersisted(pid, 2, classOf[C])
+      }
+
+      val li = receivePersisted(pid, 2, classOf[B])
+      (li should contain).theSameElementsInOrderAs(List(B(1), B(2)))
+    }
+
+    "successfully set and execute custom policy" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val newPolicy = new EventStorage.JournalPolicies.PolicyType {
+        override def tryProcess(persistenceId: String, processingUnit: JournalOperation): ProcessingResult = {
+          processingUnit match {
+            case WriteEvents(msgs) =>
+              val ex = msgs.exists({
+                case B(666) => true
+                case _      => false
+              })
+              if (ex) {
+                ProcessingSuccess
+              } else {
+                StorageFailure(err)
+              }
+            case _ => ProcessingSuccess
+          }
+        }
+      }
+
+      withPolicy(newPolicy)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      watch(a)
+      expectTerminated(a)
+
+      val aa = system.actorOf(Props(classOf[A], pid, None))
+
+      aa ! B(666)
+
+      expectNextPersisted(pid, B(666))
+
+      returnDefaultPolicy()
+
+    }
+
+    "reject next persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      //consecutive calls should stack
+      rejectNextPersisted()
+      rejectNextPersisted()
+
+      a ! B(1)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(1))
+      }
+
+      a ! B(2)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(2))
+      }
+
+      a ! B(3)
+
+      expectNextPersisted(pid, B(3))
+
+    }
+
+    "reject next persisted with custom exception" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      val err = new Exception("Custom ERROR!")
+
+      rejectNextPersisted(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      a ! B(2)
+
+      expectNextPersisted(pid, B(2))
+
+    }
+
+    "fail next persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      //consecutive calls should stack
+      failNextPersisted()
+      failNextPersisted()
+
+      a ! B(1)
+
+      watch(a)
+      expectTerminated(a)
+
+      val b = system.actorOf(Props(classOf[A], pid, None))
+
+      b ! B(2)
+
+      watch(b)
+      expectTerminated(b)
+
+      val c = system.actorOf(Props(classOf[A], pid, None))
+
+      c ! B(3)
+
+      expectNextPersisted(pid, B(3))
+
+    }
+
+    "fail next persisted with custom exception" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      val err = new Exception("Custom ERROR!")
+
+      failNextPersisted(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "expect nothingPersisted fails" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! B(1)
+
+      assertThrows[AssertionError] {
+        expectNothingPersisted(pid)
+      }
+
+    }
+
+    "expect no message persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! B(1)
+
+      expectNextPersisted(pid, B(1))
+
+      expectNothingPersisted(pid)
+
+    }
+
+    "fail recovery" in {
+
+      val pid = randomPid()
+
+      failNextNOps(1)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      watch(a)
+
+      expectTerminated(a)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+    }
+
+    "recover persisted messages" in {
+
+      val preload = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((preload.asScala, 0))
+
+    }
+
+    "fail to recover persisted messages for any actor" in {
+
+      val preload = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      failNextRead()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "fail to recover persisted messages for any actor with custom error" in {
+
+      val preload = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+        watch(a)
+        expectTerminated(a)
+      }
+
+    }
+
+    "fail to recover persisted messages for actor with particular persistenceId" in {
+
+      val preload = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(pid)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "recover persisted messages when fail for different persistenceId is set" in {
+
+      val preload = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      val otherPid = randomPid()
+
+      failNextRead(otherPid)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((preload.asScala, 0))
+
+    }
+
+    "persist and return persisted messages" in {
+
+      val pid = randomPid()
+
+      val saved = List(B(1), B(2), B(3)).map(e => e: Any).asJava
+
+      persistForRecovery(pid, saved)
+
+      val li = persistedInStorage(pid).asScala
+
+      (li should contain).theSameElementsInOrderAs(saved.asScala)
+
+    }
+
+    "fail next delete for any actor" in {
+
+      val pid = randomPid()
+
+      val preload = List(B(1)).map(e => e: Any).asJava
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete()
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload.asScala, 0))
+      expectMsgPF() { case DeleteMessagesFailure(ExpectedFailure, _) => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "fail next delete for any actor with custom exception" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val preload = List(B(1)).map(e => e: Any).asJava
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(err)
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload.asScala, 0))
+      expectMsgPF() { case DeleteMessagesFailure(e, _) if e.getMessage == err.getMessage => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "fail next delete for particular persistence id" in {
+
+      val pid = randomPid()
+
+      val preload = List(B(1)).map(e => e: Any).asJava
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(pid)
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload.asScala, 0))
+      expectMsgPF() { case DeleteMessagesFailure(ExpectedFailure, _) => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "not fail next delete for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(1).map(e => e: Any).asJava)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val other = randomPid()
+
+      failNextDelete(other)
+
+      a ! DeleteAllMessages
+
+      expectMsg((List(1), 0))
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "clear all" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)).map(e => e: Any).asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearAll()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "clear all for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)).map(e => e: Any).asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByPersistenceId(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "preserve all for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)).map(e => e: Any).asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByPersistenceId(randomPid())
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+    }
+
+    "clear all preserving seq nums" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)).map(e => e: Any).asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearAllPreservingSeqNumbers()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(3L)
+
+    }
+
+    "clear all preserving seq num for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)).map(e => e: Any).asJava)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByIdPreservingSeqNumbers(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(3L)
+
+    }
+
+    specificTests()
+
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/JavaDslUtils.scala

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import java.util
+
+import akka.actor.typed.ActorRef
+import akka.persistence.typed.javadsl.{ CommandHandler, EventHandler, EventSourcedBehavior, SignalHandler }
+import akka.persistence.testkit.{ Cmd, CommonUtils, EmptyState, Evt, Passivate, Recovered, Stopped, TestCommand }
+import akka.persistence.typed.{ PersistenceId, RecoveryCompleted }
+
+trait JavaDslUtils extends CommonUtils {
+
+  def eventSourcedBehavior(
+      pid: String,
+      setConstantTag: Boolean = false,
+      replyOnRecovery: Option[ActorRef[Any]] = None) =
+    new EventSourcedBehavior[TestCommand, Evt, EmptyState](PersistenceId.ofUniqueId(pid)) {
+
+      override protected def emptyState: EmptyState = EmptyState()
+
+      override protected def commandHandler(): CommandHandler[TestCommand, Evt, EmptyState] =
+        newCommandHandlerBuilder()
+          .forAnyState()
+          .onAnyCommand((command: TestCommand) => {
+            command match {
+              case Cmd(data) => Effect.persist(Evt(data))
+              case Passivate => Effect.stop().thenRun((_: EmptyState) => replyOnRecovery.foreach(_ ! Stopped))
+            }
+          })
+
+      override protected def eventHandler(): EventHandler[EmptyState, Evt] =
+        newEventHandlerBuilder().forAnyState().onAnyEvent(_ => emptyState)
+
+      override def shouldSnapshot(state: EmptyState, event: Evt, sequenceNr: Long): Boolean = true
+
+      override def signalHandler(): SignalHandler[EmptyState] =
+        newSignalHandlerBuilder().onSignal(RecoveryCompleted, _ => replyOnRecovery.foreach(_ ! Recovered)).build
+
+      override def tagsFor(event: Evt): util.Set[String] = {
+        if (setConstantTag) {
+          util.Collections.singleton("tag")
+        } else {
+          super.tagsFor(event)
+        }
+      }
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/SnapshotNotSerializeSpec.scala

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class SnapshotNotSerializeSpec extends CommonSnapshotTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("SnapshotNotSerializeSpec", false, false)
+
+  import testKit._
+
+  override def specificTests(): Unit =
+    "succeed if trying to save nonserializable snapshot" in {
+      val pid = randomPid()
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+      val c = new C
+      a ! NewSnapshot(c)
+
+      expectNextPersisted(pid, c)
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/SnapshotSerializeSpec.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import java.io.NotSerializableException
+
+import akka.actor.Props
+import akka.persistence.SaveSnapshotFailure
+import akka.persistence.testkit._
+
+class SnapshotSerializeSpec extends CommonSnapshotTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("SnapshotSerializeSpec", true, true)
+
+  override def specificTests(): Unit =
+    "fail if tries to save nonserializable snapshot" in {
+      val pid = randomPid()
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+      a ! NewSnapshot(new C)
+
+      expectMsg((List.empty, 0L))
+      expectMsgPF() { case SaveSnapshotFailure(_, _: NotSerializableException) => }
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/TestKitNotSerializeSpec.scala

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class TestKitNotSerializeSpec extends CommonTestKitTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("TestKitNotSerializeSpec", false, false)
+
+  import testKit._
+
+  override def specificTests() = "save next nonserializable persisted" in {
+    val pid = randomPid()
+    val a = system.actorOf(Props(classOf[A], pid, None))
+    val c = new C
+    a ! c
+
+    expectNextPersisted(pid, c)
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/javadsl/TestKitSerializeSpec.scala

@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.javadsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class TestKitSerializeSpec extends CommonTestKitTests {
+  override lazy val system = initSystemWithEnabledPlugin("TestKitSerializeSpec", true, true)
+
+  override def specificTests(): Unit = "fail next nonserializable persisted" in {
+    val pid = randomPid()
+    val a = system.actorOf(Props(classOf[A], pid, None))
+    a ! new C
+
+    watch(a)
+    expectTerminated(a)
+  }
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/CommonSnapshotTests.scala

@@ -0,0 +1,497 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.Props
+import akka.persistence._
+import akka.persistence.testkit._
+import akka.testkit.EventFilter
+import org.scalatest.matchers.should.Matchers._
+import akka.actor.typed.scaladsl.adapter._
+
+trait CommonSnapshotTests extends ScalaDslUtils {
+
+  lazy val testKit = new SnapshotTestKit(system)
+  import testKit._
+
+  def specificTests(): Unit
+
+  "SnapshotTestKit" should {
+
+    "work with typed actors" in {
+      val pid = randomPid()
+      val act = system.spawn(eventSourcedBehavior(pid), pid)
+      act ! Cmd("")
+      testKit.expectNextPersisted(pid, EmptyState())
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "save snapshot" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(1: Any)
+      a ! NewSnapshot(2: Any)
+
+      expectNextPersisted(pid, 1)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, 3)
+      }
+
+      expectNextPersisted(pid, 2)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, 3)
+      }
+
+    }
+
+    "save snapshot and check type" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(1: Any)
+      a ! NewSnapshot(2: Any)
+
+      expectNextPersistedType[Int](pid) should be(1)
+
+      assertThrows[AssertionError] {
+        expectNextPersistedType[String](pid)
+      }
+
+      expectNextPersistedType[Int](pid) should be(2)
+
+      assertThrows[AssertionError] {
+        expectNextPersistedType(pid)
+      }
+    }
+
+    "successfully set and execute custom policy" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val newPolicy = new SnapshotStorage.SnapshotPolicies.PolicyType {
+        override def tryProcess(persistenceId: String, processingUnit: SnapshotOperation): ProcessingResult = {
+          processingUnit match {
+            case WriteSnapshot(_, msgs) =>
+              val ex = msgs match {
+                case 777 => true
+                case _   => false
+              }
+              if (ex) {
+                ProcessingSuccess
+              } else {
+                StorageFailure(err)
+              }
+            case _ => ProcessingSuccess
+          }
+        }
+      }
+
+      withPolicy(newPolicy)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ee) if ee.getMessage == err.getMessage => }
+
+      a ! NewSnapshot(777)
+
+      expectMsgPF() { case SaveSnapshotSuccess(_) => }
+      expectNextPersisted(pid, 777)
+
+      returnDefaultPolicy()
+
+    }
+
+    "expect next N valid snapshots in order" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(1)
+      a ! NewSnapshot(2)
+
+      assertThrows[AssertionError] {
+        receivePersisted[Int](pid, 3)
+      }
+      assertThrows[AssertionError] {
+        receivePersisted[String](pid, 2)
+      }
+      val li = receivePersisted[Int](pid, 2)
+      (li should contain).theSameElementsInOrderAs(List(1, 2))
+    }
+
+    "fail when receives wrong type" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! NewSnapshot(1)
+      a ! NewSnapshot("data")
+      assertThrows[AssertionError] {
+        receivePersisted[Int](pid, 2)
+      }
+    }
+
+    "fail next snapshot" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      //consecutive calls should stack
+      failNextPersisted()
+      failNextPersisted()
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ExpectedFailure) => }
+
+      val b = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      b ! NewSnapshot(2)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ExpectedFailure) => }
+
+      val c = system.actorOf(Props(classOf[A], pid, None))
+
+      c ! NewSnapshot(3)
+
+      expectNextPersisted(pid, 3)
+
+    }
+
+    "fail next snapshot with custom error" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val err = new Exception("Custom ERROR!")
+
+      failNextPersisted(err)
+
+      a ! NewSnapshot(1)
+
+      expectMsg((List.empty, 0))
+      expectMsgPF() { case SaveSnapshotFailure(_, ee) if err.getMessage == ee.getMessage => }
+
+    }
+
+    "expect nothingPersisted fails" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! NewSnapshot(1)
+
+      assertThrows[AssertionError] {
+        expectNothingPersisted(pid)
+      }
+
+    }
+
+    "expect no snapshot persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! NewSnapshot(1)
+
+      expectNextPersisted(pid, 1)
+
+      expectNothingPersisted(pid)
+
+    }
+
+    "fail recovery" in {
+
+      val pid = randomPid()
+
+      failNextNOps(1)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      watch(a)
+
+      expectTerminated(a)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+    }
+
+    "recover last persisted snapshot" in {
+
+      val pid = randomPid()
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      persistForRecovery(pid, preload)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    "fail to recover persisted snapshots for any actor" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      persistForRecovery(pid, preload)
+
+      failNextRead()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "fail to recover persisted snapshots for any actor with custom error" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      val err = new Exception("Custom ERROR!")
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+        watch(a)
+        expectTerminated(a)
+      }
+
+    }
+
+    "fail to recover persisted snapshots for actor with particular persistenceId" in {
+
+      val pid = randomPid()
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(pid)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "recover last persisted snapshot when fail for different persistenceId is set" in {
+
+      val pid = randomPid()
+
+      val preload = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      persistForRecovery(pid, preload)
+
+      val otherPid = randomPid()
+
+      failNextRead(otherPid)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    "persist and return persisted snapshots" in {
+
+      val pid = randomPid()
+
+      val saved = List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3))
+
+      persistForRecovery(pid, saved)
+
+      val li = persistedInStorage(pid)
+
+      (li should contain).theSameElementsInOrderAs(saved)
+
+    }
+
+    "fail next snapshot delete for any actor" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1)))
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete()
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 1))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ExpectedFailure) => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "fail next snapshot delete for any actor with custom error" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1)))
+
+      val err = new Exception("Custom ERROR!")
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(err)
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 1))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ee) if ee.getMessage == err.getMessage => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "fail next delete for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3)))
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(pid)
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsg((List.empty, 3))
+      expectMsgPF() { case DeleteSnapshotFailure(_, ExpectedFailure) => }
+
+      a ! DeleteSomeSnapshot(0)
+
+      expectMsgPF() { case DeleteSnapshotSuccess(meta) if meta.sequenceNr == 0 => }
+      expectNoMessage()
+
+    }
+
+    "not fail next delete for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3)))
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val other = randomPid()
+
+      failNextDelete(other)
+
+      a ! DeleteSomeSnapshotByCriteria(SnapshotSelectionCriteria.Latest)
+
+      expectMsg((List.empty, 3))
+      expectMsgPF() { case DeleteSnapshotsSuccess(SnapshotSelectionCriteria.Latest) => }
+
+    }
+
+    "clear all" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearAll()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskSnapshotSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "clear all for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearByPersistenceId(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskSnapshotSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "preserve all for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List((SnapshotMeta(0), 1), (SnapshotMeta(1), 2), (SnapshotMeta(2), 3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+      clearByPersistenceId(randomPid())
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 3))
+
+    }
+
+    specificTests()
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/CommonTestKitTests.scala

@@ -0,0 +1,596 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.Props
+import akka.persistence.{ DeleteMessagesFailure, DeleteMessagesSuccess }
+import akka.testkit.EventFilter
+import akka.persistence.testkit._
+import org.scalatest.matchers.should.Matchers._
+import akka.actor.typed.scaladsl.adapter._
+
+trait CommonTestKitTests extends ScalaDslUtils {
+
+  lazy val testKit = new PersistenceTestKit(system)
+  import testKit._
+
+  def specificTests(): Unit
+
+  "PersistenceTestKit" should {
+
+    "work with typed actors" in {
+      val expectedId = randomPid()
+      val pid = randomPid()
+      val act = system.spawn(eventSourcedBehavior(pid), pid)
+      act ! Cmd(expectedId)
+
+      testKit.expectNextPersisted(pid, Evt(expectedId))
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "work with tagged events" in {
+      val expectedId = randomPid()
+      val pid = randomPid()
+      var act =
+        system.spawn(eventSourcedBehavior(pid, Some(testActor.toTyped[Any])).withTagger(_ => Set("tag")), randomPid())
+      expectMsg(Recovered)
+      act ! Cmd(expectedId)
+      testKit.expectNextPersisted(pid, Evt(expectedId))
+      act ! Passivate
+      expectMsg(Stopped)
+
+      act =
+        system.spawn(eventSourcedBehavior(pid, Some(testActor.toTyped[Any])).withTagger(_ => Set("tag")), randomPid())
+      val expectedId2 = randomPid()
+      act ! Cmd(expectedId2)
+      expectMsg(Recovered)
+      testKit.expectNextPersisted(pid, Evt(expectedId2))
+      testKit.expectNothingPersisted(pid)
+    }
+
+    "expect next valid message" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! B(1)
+      a ! B(2)
+
+      expectNextPersisted(pid, B(1))
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(3))
+      }
+
+      expectNextPersisted(pid, B(2))
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(3))
+      }
+
+    }
+
+    "expect next valid message and check type" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! B(1)
+      a ! B(2)
+
+      expectNextPersistedType[B](pid)
+      assertThrows[AssertionError] {
+        expectNextPersistedType[A](pid)
+      }
+      expectNextPersistedType[B](pid)
+      assertThrows[AssertionError] {
+        expectNextPersistedType[B](pid)
+      }
+    }
+
+    "expect next N valid messages in order" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      a ! B(1)
+      a ! B(2)
+
+      assertThrows[AssertionError] {
+        receivePersisted[B](pid, 3)
+      }
+      assertThrows[AssertionError] {
+        receivePersisted[C](pid, 2)
+      }
+      val li = receivePersisted[B](pid, 2)
+      (li should contain).theSameElementsInOrderAs(List(B(1), B(2)))
+    }
+
+    "successfully set and execute custom policy" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val newPolicy = new EventStorage.JournalPolicies.PolicyType {
+        override def tryProcess(persistenceId: String, processingUnit: JournalOperation): ProcessingResult = {
+          processingUnit match {
+            case WriteEvents(msgs) =>
+              val ex = msgs.exists({
+                case B(666) => true
+                case _      => false
+              })
+              if (ex) {
+                ProcessingSuccess
+              } else {
+                StorageFailure(err)
+              }
+            case _ => ProcessingSuccess
+          }
+        }
+      }
+
+      withPolicy(newPolicy)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      watch(a)
+      expectTerminated(a)
+
+      val aa = system.actorOf(Props(classOf[A], pid, None))
+      aa ! B(666)
+
+      expectNextPersisted(pid, B(666))
+      returnDefaultPolicy()
+
+    }
+
+    "reject next persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      //consecutive calls should stack
+      rejectNextPersisted()
+      rejectNextPersisted()
+
+      a ! B(1)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(1))
+      }
+
+      a ! B(2)
+
+      assertThrows[AssertionError] {
+        expectNextPersisted(pid, B(2))
+      }
+
+      a ! B(3)
+
+      expectNextPersisted(pid, B(3))
+
+    }
+
+    "reject next persisted with custom exception" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      val err = new Exception("Custom ERROR!")
+
+      rejectNextPersisted(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      a ! B(2)
+
+      expectNextPersisted(pid, B(2))
+
+    }
+
+    "fail next persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      //consecutive calls should stack
+      failNextPersisted()
+      failNextPersisted()
+
+      a ! B(1)
+
+      watch(a)
+      expectTerminated(a)
+
+      val b = system.actorOf(Props(classOf[A], pid, None))
+
+      b ! B(2)
+
+      watch(b)
+      expectTerminated(b)
+
+      val c = system.actorOf(Props(classOf[A], pid, None))
+
+      c ! B(3)
+
+      expectNextPersisted(pid, B(3))
+
+    }
+
+    "fail next persisted with custom exception" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      val err = new Exception("Custom ERROR!")
+
+      failNextPersisted(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        a ! B(1)
+      }
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "expect nothingPersisted fails" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! B(1)
+
+      assertThrows[AssertionError] {
+        expectNothingPersisted(pid)
+      }
+
+    }
+
+    "expect no message persisted" in {
+
+      val pid = randomPid()
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      expectNothingPersisted(pid)
+
+      a ! B(1)
+
+      expectNextPersisted(pid, B(1))
+
+      expectNothingPersisted(pid)
+
+    }
+
+    "fail recovery" in {
+
+      val pid = randomPid()
+
+      failNextNOps(1)
+
+      val a = system.actorOf(Props(classOf[A], pid, None))
+
+      watch(a)
+
+      expectTerminated(a)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+    }
+
+    "recover persisted messages" in {
+
+      val preload = List(B(1), B(2), B(3))
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((preload, 0))
+
+    }
+
+    "fail to recover persisted messages for any actor" in {
+
+      val preload = List(B(1), B(2), B(3))
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      failNextRead()
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "fail to recover persisted messages for any actor with custom error" in {
+
+      val preload = List(B(1), B(2), B(3))
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(err)
+
+      EventFilter.error(err.getMessage, occurrences = 1).intercept {
+        val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+        watch(a)
+        expectTerminated(a)
+      }
+
+    }
+
+    "fail to recover persisted messages for actor with particular persistenceId" in {
+
+      val preload = List(B(1), B(2), B(3))
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      failNextRead(pid)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      watch(a)
+      expectTerminated(a)
+
+    }
+
+    "recover persisted messages when fail for different persistenceId is set" in {
+
+      val preload = List(B(1), B(2), B(3))
+      val pid = randomPid()
+
+      persistForRecovery(pid, preload)
+
+      val otherPid = randomPid()
+
+      failNextRead(otherPid)
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((preload, 0))
+
+    }
+
+    "persist and return persisted messages" in {
+
+      val pid = randomPid()
+
+      val saved = List(B(1), B(2), B(3))
+
+      persistForRecovery(pid, saved)
+
+      val li = persistedInStorage(pid)
+
+      (li should contain).theSameElementsInOrderAs(saved)
+
+    }
+
+    "fail next delete for any actor" in {
+
+      val pid = randomPid()
+
+      val preload = List(B(1))
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete()
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload, 0))
+      expectMsgPF() { case DeleteMessagesFailure(ExpectedFailure, _) => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "fail next delete for any actor with custom exception" in {
+
+      val pid = randomPid()
+
+      val err = new Exception("BOOM!")
+
+      val preload = List(B(1))
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(err)
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload, 0))
+      expectMsgPF() { case DeleteMessagesFailure(e, _) if e.getMessage == err.getMessage => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "fail next delete for particular persistence id" in {
+
+      val pid = randomPid()
+
+      val preload = List(B(1))
+      persistForRecovery(pid, preload)
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      failNextDelete(pid)
+
+      a ! DeleteAllMessages
+
+      expectMsg((preload, 0))
+      expectMsgPF() { case DeleteMessagesFailure(ExpectedFailure, _) => }
+
+      a ! DeleteAllMessages
+
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "not fail next delete for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(1))
+
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      val other = randomPid()
+
+      failNextDelete(other)
+
+      a ! DeleteAllMessages
+
+      expectMsg((List(1), 0))
+      expectMsgPF() { case DeleteMessagesSuccess(_) => }
+
+    }
+
+    "clear all" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearAll()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "clear all for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByPersistenceId(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(0L)
+
+    }
+
+    "preserve all for other persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByPersistenceId(randomPid())
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+    }
+
+    "clear all preserving seq nums" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearAllPreservingSeqNumbers()
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(3L)
+
+    }
+
+    "clear all preserving seq num for particular persistence id" in {
+
+      val pid = randomPid()
+
+      persistForRecovery(pid, List(B(1), B(2), B(3)))
+
+      system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List(B(1), B(2), B(3)), 0))
+
+      clearByIdPreservingSeqNumbers(pid)
+
+      val aa = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+
+      expectMsg((List.empty, 0))
+
+      aa ! AskMessageSeqNum
+
+      expectMsg(3L)
+
+    }
+
+    specificTests()
+
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/PersistenceTestKitJournalCompatSpec.scala

@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import java.io.NotSerializableException
+
+import akka.persistence.CapabilityFlag
+import akka.persistence.journal.JournalSpec
+import akka.persistence.snapshot.SnapshotStoreSpec
+import akka.persistence.testkit._
+import akka.persistence.testkit.EventStorage.JournalPolicies
+import akka.persistence.testkit.Reject
+import akka.persistence.testkit.internal.InMemStorageExtension
+
+class PersistenceTestKitJournalCompatSpec extends JournalSpec(config = PersistenceTestKitPlugin.config) {
+
+  override def beforeAll(): Unit = {
+    super.beforeAll()
+    InMemStorageExtension(system).setPolicy(new JournalPolicies.PolicyType {
+      override def tryProcess(persistenceId: String, op: JournalOperation): ProcessingResult = {
+        op match {
+          case WriteEvents(batch) =>
+            val allSerializable =
+              batch.filter(_.isInstanceOf[AnyRef]).forall(_.isInstanceOf[java.io.Serializable])
+            if (allSerializable) {
+              ProcessingSuccess
+            } else {
+              Reject(new NotSerializableException("Some objects in the batch were not serializable"))
+            }
+          case _ => ProcessingSuccess
+        }
+
+      }
+    })
+  }
+
+  override protected def supportsRejectingNonSerializableObjects: CapabilityFlag = true
+}
+
+class PersistenceTestKitSnapshotStoreCompatSpec
+    extends SnapshotStoreSpec(config = PersistenceTestKitSnapshotPlugin.config)

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/ScalaDslUtils.scala

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.typed.ActorRef
+import akka.persistence.typed.RecoveryCompleted
+import akka.persistence.typed.scaladsl.{ Effect, EventSourcedBehavior }
+import akka.persistence.testkit.{ Cmd, CommonUtils, EmptyState, Evt, Passivate, Recovered, Stopped, TestCommand }
+import akka.persistence.typed.PersistenceId
+
+trait ScalaDslUtils extends CommonUtils {
+
+  def eventSourcedBehavior(pid: String, replyOnRecovery: Option[ActorRef[Any]] = None) =
+    EventSourcedBehavior[TestCommand, Evt, EmptyState](PersistenceId.ofUniqueId(pid), EmptyState(), (_, cmd) => {
+      cmd match {
+        case Cmd(data) => Effect.persist(Evt(data))
+        case Passivate => Effect.stop().thenRun(_ => replyOnRecovery.foreach(_ ! Stopped))
+      }
+    }, (_, _) => EmptyState()).snapshotWhen((_, _, _) => true).receiveSignal {
+      case (_, RecoveryCompleted) => replyOnRecovery.foreach(_ ! Recovered)
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/SnapshotNotSerializeSpec.scala

@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class SnapshotNotSerializeSpec extends CommonSnapshotTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("SnapshotNotSerializeSpec", false, false)
+
+  import testKit._
+
+  override def specificTests(): Unit =
+    "succeed if trying to save nonserializable snapshot" in {
+      val pid = randomPid()
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+      val c = new C
+      a ! NewSnapshot(c)
+
+      expectNextPersisted(pid, c)
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/SnapshotSerializeSpec.scala

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2019-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import java.io.NotSerializableException
+
+import akka.actor.Props
+import akka.persistence.SaveSnapshotFailure
+import akka.persistence.testkit._
+
+class SnapshotSerializeSpec extends CommonSnapshotTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("SnapshotSerializeSpec", true, true)
+
+  override def specificTests(): Unit =
+    "fail if tries to save nonserializable snapshot" in {
+      val pid = randomPid()
+      val a = system.actorOf(Props(classOf[A], pid, Some(testActor)))
+      a ! NewSnapshot(new C)
+
+      expectMsg((List.empty, 0L))
+      expectMsgPF() { case SaveSnapshotFailure(_, _: NotSerializableException) => }
+    }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/TestKitNotSerializeSpec.scala

@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class TestKitNotSerializeSpec extends CommonTestKitTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("TestKitNotSerializeSpec", false, false)
+
+  import testKit._
+
+  override def specificTests() = "save next nonserializable persisted" in {
+    val pid = randomPid()
+    val a = system.actorOf(Props(classOf[A], pid, None))
+    val c = new C
+    a ! c
+
+    expectNextPersisted(pid, c)
+  }
+
+}

akka-persistence-testkit/src/test/scala/akka/persistence/testkit/scaladsl/TestKitSerializeSpec.scala

@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2018-2020 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.persistence.testkit.scaladsl
+
+import akka.actor.Props
+import akka.persistence.testkit._
+
+class TestKitSerializeSpec extends CommonTestKitTests {
+
+  override lazy val system = initSystemWithEnabledPlugin("TestKitSerializeSpec", true, true)
+
+  override def specificTests(): Unit = "fail next nonserializable persisted" in {
+    val pid = randomPid()
+    val a = system.actorOf(Props(classOf[A], pid, None))
+    a ! new C
+
+    watch(a)
+    expectTerminated(a)
+  }
+}

akka-testkit/src/main/scala/akka/testkit/TestKit.scala

@@ -345,6 +345,44 @@ trait TestKitBase {
     poll(_max min interval)
   }
 
+  /**
+   * Evaluate the given assert every `interval` until exception is thrown or `max` timeout is expired.
+   *
+   * Returns the result of last evaluation of the assertion.
+   *
+   * If no timeout is given, take it from the innermost enclosing `within`
+   * block.
+   *
+   * Note that the timeout is scaled using Duration.dilated,
+   * which uses the configuration entry "akka.test.timefactor".
+   */
+  def assertForDuration[A](a: => A, max: FiniteDuration, interval: Duration = 100.millis): A = {
+    val _max = remainingOrDilated(max)
+    val stop = now + _max
+
+    @tailrec
+    def poll(t: Duration): A = {
+      // cannot use null-ness of result as signal it failed
+      // because Java API and not wanting to return a value will be "return null"
+      val instantNow = now
+      val result =
+        try {
+          a
+        } catch {
+          case e: Throwable => throw e
+        }
+
+      if (instantNow < stop) {
+        Thread.sleep(t.toMillis)
+        poll((stop - now) min interval)
+      } else {
+        result
+      }
+    }
+
+    poll(max min interval)
+  }
+
   /**
    * Execute code block while bounding its execution time between `min` and
    * `max`. `within` blocks may be nested. All methods in this trait which

akka-testkit/src/main/scala/akka/testkit/javadsl/TestKit.scala

@@ -8,6 +8,7 @@ import java.util.function.{ Supplier, Function => JFunction }
 import java.util.{ List => JList }
 
 import akka.actor._
+import akka.annotation.InternalApi
 import akka.testkit.{ TestActor, TestDuration, TestProbe }
 import akka.util.JavaDurationConverters._
 
@@ -931,7 +932,8 @@ object TestKit {
  * This class is used internal to [[akka.testkit.javadsl.TestKit]] and
  * should not be extended by client code directly.
  */
-private abstract class CachingPartialFunction[A, B] extends scala.runtime.AbstractPartialFunction[A, B] {
+@InternalApi
+private[akka] abstract class CachingPartialFunction[A, B] extends scala.runtime.AbstractPartialFunction[A, B] {
   import akka.japi.JavaPartialFunction._
 
   @throws(classOf[Exception])

build.sbt

@@ -60,6 +60,7 @@ lazy val aggregatedProjects: Seq[ProjectReference] = List[ProjectReference](
   persistenceShared,
   persistenceTck,
   persistenceTyped,
+  persistenceTestkit,
   protobuf,
   protobufV3,
   remote,
@@ -194,7 +195,8 @@ lazy val docs = akkaModule("akka-docs")
     clusterTyped % "compile->compile;test->test",
     clusterShardingTyped % "compile->compile;test->test",
     actorTypedTests % "compile->compile;test->test",
-    streamTestkit % "compile->compile;test->test")
+    streamTestkit % "compile->compile;test->test",
+    persistenceTestkit % "compile->compile;test->test")
   .settings(Dependencies.docs)
   .settings(Paradox.settings)
   .settings(ParadoxSupport.paradoxWithCustomDirectives)
@@ -268,6 +270,12 @@ lazy val persistenceTck = akkaModule("akka-persistence-tck")
   .settings(fork in Test := true)
   .disablePlugins(MimaPlugin)
 
+lazy val persistenceTestkit = akkaModule("akka-persistence-testkit")
+  .dependsOn(persistenceTyped % "compile->compile;provided->provided;test->test", testkit % "compile->compile;test->test", persistenceTck % "test")
+  .settings(Dependencies.persistenceTestKit)
+  .settings(AutomaticModuleName.settings("akka.persistence.testkit"))
+  .disablePlugins(MimaPlugin)
+
 lazy val protobuf = akkaModule("akka-protobuf")
   .settings(OSGi.protobuf)
   .settings(AutomaticModuleName.settings("akka.protobuf"))

project/Dependencies.scala

@@ -242,6 +242,8 @@ object Dependencies {
         Provided.levelDB,
         Provided.levelDBNative)
 
+  val persistenceTestKit = l ++= Seq(Test.scalatest.value)
+
   val persistenceShared = l ++= Seq(Provided.levelDB, Provided.levelDBNative)
 
   val jackson = l ++= Seq(