+per #13815 akka-persistence-tck based on @krasserm's work

Original here: https://github.com/krasserm/akka-persistence-testkit

New features:
* merged martin's tests
* usable from java (junit 4)
* simple bench test, which helps checking if ordering is perserved under
  bigger workloads and simple perf checking
* does NOT include tests for already deprecated features (deleteMessages)
* docs

Resolves #13815

Conflicts:
	project/AkkaBuild.scala

akka-docs/rst/java/code/docs/persistence/PersistencePluginDocTest.java

@@ -5,17 +5,27 @@
 package docs.persistence;
 
 //#plugin-imports
-import akka.actor.UntypedActor;
-import scala.concurrent.Future;
+
+import akka.actor.*;
 import akka.japi.Option;
 import akka.japi.Procedure;
 import akka.persistence.*;
-import akka.persistence.journal.japi.*;
-import akka.persistence.snapshot.japi.*;
-//#plugin-imports
-import akka.actor.*;
+import akka.persistence.japi.journal.JavaJournalSpec;
+import akka.persistence.japi.snapshot.JavaSnapshotStoreSpec;
+import akka.persistence.journal.japi.AsyncWriteJournal;
 import akka.persistence.journal.leveldb.SharedLeveldbJournal;
 import akka.persistence.journal.leveldb.SharedLeveldbStore;
+import akka.persistence.snapshot.japi.SnapshotStore;
+import com.typesafe.config.Config;
+import com.typesafe.config.ConfigFactory;
+import org.iq80.leveldb.util.FileUtils;
+import scala.concurrent.Future;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+
+//#plugin-imports
 
 public class PersistencePluginDocTest {
 
@@ -106,4 +116,68 @@ public class PersistencePluginDocTest {
             return null;
         }
     }
+
+
+    static Object o2 = new Object() {
+        //#journal-tck-java
+        class MyJournalSpecTest extends JavaJournalSpec {
+
+            public MyJournalSpecTest() {
+                super(ConfigFactory.parseString(
+                        "persistence.journal.plugin = " +
+                        "\"akka.persistence.journal.leveldb-shared\""));
+            }
+        }
+        //#journal-tck-java
+    };
+
+    static Object o3 = new Object() {
+        //#snapshot-store-tck-java
+        class MySnapshotStoreTest extends JavaSnapshotStoreSpec {
+
+            public MySnapshotStoreTest() {
+                super(ConfigFactory.parseString(
+                        "akka.persistence.snapshot-store.plugin = " +
+                        "\"akka.persistence.snapshot-store.local\""));
+            }
+        }
+        //#snapshot-store-tck-java
+    };
+
+    static Object o4 = new Object() {
+        //#journal-tck-before-after-java
+        class MyJournalSpecTest extends JavaJournalSpec {
+
+            List<File> storageLocations = new ArrayList<File>();
+
+            public MyJournalSpecTest() {
+                super(ConfigFactory.parseString(
+                        "persistence.journal.plugin = " +
+                        "\"akka.persistence.journal.leveldb-shared\""));
+
+                Config config = system().settings().config();
+                storageLocations.add(new File(
+                    config.getString("akka.persistence.journal.leveldb.dir")));
+                storageLocations.add(new File(
+                    config.getString("akka.persistence.snapshot-store.local.dir")));
+            }
+
+            @Override
+            public void beforeAll() {
+                for (File storageLocation : storageLocations) {
+                    FileUtils.deleteRecursively(storageLocation);
+                }
+                super.beforeAll();
+            }
+
+            @Override
+            public void afterAll() {
+                super.afterAll();
+                for (File storageLocation : storageLocations) {
+                    FileUtils.deleteRecursively(storageLocation);
+                }
+            }
+        }
+        //#journal-tck-before-after-java
+    };
 }

akka-docs/rst/java/persistence.rst

@@ -498,6 +498,40 @@ A snapshot store plugin can be activated with the following minimal configuratio
 The specified plugin ``class`` must have a no-arg constructor. The ``plugin-dispatcher`` is the dispatcher
 used for the plugin actor. If not specified, it defaults to ``akka.persistence.dispatchers.default-plugin-dispatcher``.
 
+Plugin TCK
+----------
+In order to help developers build correct and high quality storage plugins, we provide an Technology Compatibility Kit (`TCK <http://en.wikipedia.org/wiki/Technology_Compatibility_Kit>`_ for short).
+
+The TCK is usable from Java as well as Scala projects, for Java you need to include the akka-persistence-tck-experimental dependency::
+
+  <dependency>
+    <groupId>com.typesafe.akka</groupId>
+    <artifactId>akka-persistence-tck-experimental_${scala.version}</artifactId>
+    <version>2.3.5</version>
+    <scope>test</scope>
+  </dependency>
+
+To include the Journal TCK tests in your test suite simply extend the provided ``JavaJournalSpec``:
+
+.. includecode:: ./code/docs/persistence/PersistencePluginDocTest.java#journal-tck-java
+
+We also provide a simple benchmarking class ``JavaJournalPerfSpec`` which includes all the tests that ``JavaJournalSpec``
+has, and also performs some longer operations on the Journal while printing it's performance stats. While it is NOT aimed
+to provide a proper benchmarking environment it can be used to get a rough feel about your journals performance in the most
+typical scenarios.
+
+In order to include the ``SnapshotStore`` TCK tests in your test suite simply extend the ``SnapshotStoreSpec:
+
+.. includecode:: ./code/docs/persistence/PersistencePluginDocTest.java#snapshot-store-tck-java
+
+In case your plugin requires some setting up (starting a mock database, removing temporary files etc.) you can override the
+``beforeAll`` and ``afterAll`` methods to hook into the tests lifecycle:
+
+.. includecode:: ./code/docs/persistence/PersistencePluginDocTest.java#journal-tck-before-after-java
+
+We *highly recommend* including these specifications in your test suite, as they cover a broad range of cases you
+might have otherwise forgotten to test for when writing a plugin from scratch.
+
 Pre-packaged plugins
 ====================