diff --git a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
index 2e95c6c..d57613b 100644
--- a/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
+++ b/src/main/java/net/onrc/onos/core/topology/TopologyManager.java
@@ -59,7 +59,7 @@
     public static final String EVENT_CHANNEL_NAME = "onos.topology";
     private EventHandler eventHandler = new EventHandler();
 
-    private final TopologyDatastore datastore;
+    private TopologyDatastore datastore;
     private final TopologyImpl topology = new TopologyImpl();
     private final IControllerRegistryService registryService;
     private CopyOnWriteArrayList<ITopologyListener> topologyListeners;
@@ -1241,4 +1241,14 @@
 
         return collection;
     }
+    /**
+     * Replaces the internal datastore instance.
+     *
+     * @param dataStore instance
+     *
+     * @exclude Backdoor for unit testing purpose only, do not use.
+     */
+    void debugReplaceDataStore(final TopologyDatastore dataStoreService) {
+        this.datastore = dataStoreService;
+    }
 }