Unit tests for the distributed group store.

Change-Id: Ie8f00b9bbc1ba46a6f80e70f63d1fd853d64154b
diff --git a/core/api/src/test/java/org/onosproject/store/cluster/messaging/ClusterCommunicationServiceAdapter.java b/core/api/src/test/java/org/onosproject/store/cluster/messaging/ClusterCommunicationServiceAdapter.java
new file mode 100644
index 0000000..04f890c
--- /dev/null
+++ b/core/api/src/test/java/org/onosproject/store/cluster/messaging/ClusterCommunicationServiceAdapter.java
@@ -0,0 +1,88 @@
+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.store.cluster.messaging;
+
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+import org.onosproject.cluster.NodeId;
+
+/**
+ * Testing adapter for the cluster communication service.
+ */
+public class ClusterCommunicationServiceAdapter
+        implements ClusterCommunicationService {
+
+    @Override
+    public void addSubscriber(MessageSubject subject,
+                              ClusterMessageHandler subscriber,
+                              ExecutorService executor) {
+    }
+
+    @Override
+    public void removeSubscriber(MessageSubject subject) {}
+
+    @Override
+    public <M> void broadcast(M message, MessageSubject subject,
+                              Function<M, byte[]> encoder) {
+    }
+
+    @Override
+    public <M> void broadcastIncludeSelf(M message,
+                                         MessageSubject subject, Function<M, byte[]> encoder) {
+    }
+
+    @Override
+    public <M> CompletableFuture<Void> unicast(M message, MessageSubject subject,
+                                               Function<M, byte[]> encoder, NodeId toNodeId) {
+        return null;
+    }
+
+    @Override
+    public <M> void multicast(M message, MessageSubject subject,
+                              Function<M, byte[]> encoder, Set<NodeId> nodes) {
+    }
+
+    @Override
+    public <M, R> CompletableFuture<R> sendAndReceive(M message,
+                                                      MessageSubject subject, Function<M, byte[]> encoder,
+                                                      Function<byte[], R> decoder, NodeId toNodeId) {
+        return null;
+    }
+
+    @Override
+    public <M, R> void addSubscriber(MessageSubject subject,
+                                     Function<byte[], M> decoder, Function<M, R> handler,
+                                     Function<R, byte[]> encoder, Executor executor) {
+    }
+
+    @Override
+    public <M, R> void addSubscriber(MessageSubject subject,
+                                     Function<byte[], M> decoder, Function<M, CompletableFuture<R>> handler,
+                                     Function<R, byte[]> encoder) {
+    }
+
+    @Override
+    public <M> void addSubscriber(MessageSubject subject,
+                                  Function<byte[], M> decoder, Consumer<M> handler,
+                                  Executor executor) {
+
+    }
+}
diff --git a/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java b/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
index 5ee44c4..4f612de 100644
--- a/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
+++ b/core/api/src/test/java/org/onosproject/store/service/TestEventuallyConsistentMap.java
@@ -91,7 +91,9 @@
         EventuallyConsistentMapEvent<K, V> addEvent =
                 new EventuallyConsistentMapEvent<>(mapName, PUT, key, value);
         notifyListeners(addEvent);
-        peerUpdateFunction.apply(key, value);
+        if (peerUpdateFunction != null) {
+            peerUpdateFunction.apply(key, value);
+        }
     }
 
     @Override