Adding GroupService Adapter for Tests

Change-Id: I058a26f0f5657cee8c5aeb52d989d2d6c0dc1190
diff --git a/core/api/src/test/java/org/onosproject/net/group/GroupServiceAdapter.java b/core/api/src/test/java/org/onosproject/net/group/GroupServiceAdapter.java
new file mode 100644
index 0000000..a6b81121
--- /dev/null
+++ b/core/api/src/test/java/org/onosproject/net/group/GroupServiceAdapter.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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.net.group;
+
+import org.onosproject.core.ApplicationId;
+import org.onosproject.net.DeviceId;
+
+/**
+ * Test adapter for group service.
+ */
+public class GroupServiceAdapter implements GroupService {
+    @Override
+    public void addGroup(GroupDescription groupDesc) {
+
+    }
+
+    @Override
+    public Group getGroup(DeviceId deviceId, GroupKey appCookie) {
+        return null;
+    }
+
+    @Override
+    public void addBucketsToGroup(DeviceId deviceId, GroupKey oldCookie, GroupBuckets buckets,
+                                  GroupKey newCookie, ApplicationId appId) {
+
+    }
+
+    @Override
+    public void removeBucketsFromGroup(DeviceId deviceId, GroupKey oldCookie, GroupBuckets buckets,
+                                       GroupKey newCookie, ApplicationId appId) {
+
+    }
+
+    @Override
+    public void purgeGroupEntries(DeviceId deviceId) {
+
+    }
+
+    @Override
+    public void removeGroup(DeviceId deviceId, GroupKey appCookie, ApplicationId appId) {
+
+    }
+
+    @Override
+    public Iterable<Group> getGroups(DeviceId deviceId, ApplicationId appId) {
+        return null;
+    }
+
+    @Override
+    public Iterable<Group> getGroups(DeviceId deviceId) {
+        return null;
+    }
+
+    @Override
+    public void addListener(GroupListener listener) {
+
+    }
+
+    @Override
+    public void removeListener(GroupListener listener) {
+
+    }
+}