ONOS-5552 DocumentTree builder not available

Change-Id: Id0e9e0c647146c27e21e2ec2b2014789bbd9eca9
diff --git a/core/api/src/test/java/org/onosproject/store/service/StorageServiceAdapter.java b/core/api/src/test/java/org/onosproject/store/service/StorageServiceAdapter.java
index 01cc065..29dd72d 100644
--- a/core/api/src/test/java/org/onosproject/store/service/StorageServiceAdapter.java
+++ b/core/api/src/test/java/org/onosproject/store/service/StorageServiceAdapter.java
@@ -30,6 +30,11 @@
     }
 
     @Override
+    public <V> DocumentTreeBuilder<V> documentTreeBuilder() {
+        return null;
+    }
+
+    @Override
     public <E> DistributedSetBuilder<E> setBuilder() {
         return null;
     }