Added newValue and oldValue methods to MapEvent.

Change-Id: Ibaffc8079de03b1f4623044ec53c949831ea8cd1
diff --git a/core/api/src/test/java/org/onosproject/store/service/MapEventTest.java b/core/api/src/test/java/org/onosproject/store/service/MapEventTest.java
index 47fba6c..1015e1b 100644
--- a/core/api/src/test/java/org/onosproject/store/service/MapEventTest.java
+++ b/core/api/src/test/java/org/onosproject/store/service/MapEventTest.java
@@ -16,6 +16,7 @@
 package org.onosproject.store.service;
 
 import com.google.common.testing.EqualsTester;
+
 import org.junit.Test;
 
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -26,13 +27,14 @@
  */
 public class MapEventTest {
 
-    private final Versioned<Integer> vStats = new Versioned<>(2, 1);
+    private final Versioned<Integer> vStatsNew = new Versioned<>(2, 2);
+    private final Versioned<Integer> vStatsOld = new Versioned<>(1, 1);
 
-    private final MapEvent<String, Integer> stats1 = new MapEvent<>("a", MapEvent.Type.INSERT, "1", vStats);
+    private final MapEvent<String, Integer> stats1 = new MapEvent<>("a", "1", vStatsNew, null);
 
-    private final MapEvent<String, Integer> stats2 = new MapEvent<>("a", MapEvent.Type.REMOVE, "1", vStats);
+    private final MapEvent<String, Integer> stats2 = new MapEvent<>("a", "1", null, vStatsOld);
 
-    private final MapEvent<String, Integer> stats3 = new MapEvent<>("a", MapEvent.Type.UPDATE, "1", vStats);
+    private final MapEvent<String, Integer> stats3 = new MapEvent<>("a", "1", vStatsNew, vStatsOld);
 
     /**
      * Tests the creation of the MapEvent object.
@@ -42,7 +44,23 @@
         assertThat(stats1.name(), is("a"));
         assertThat(stats1.type(), is(MapEvent.Type.INSERT));
         assertThat(stats1.key(), is("1"));
-        assertThat(stats1.value(), is(vStats));
+        assertThat(stats1.value(), is(vStatsNew));
+        assertThat(stats1.newValue(), is(vStatsNew));
+        assertThat(stats1.oldValue(), is((Versioned<Integer>) null));
+
+        assertThat(stats2.name(), is("a"));
+        assertThat(stats2.type(), is(MapEvent.Type.REMOVE));
+        assertThat(stats2.key(), is("1"));
+        assertThat(stats2.value(), is(vStatsOld));
+        assertThat(stats2.newValue(), is((Versioned<Integer>) null));
+        assertThat(stats2.oldValue(), is(vStatsOld));
+
+        assertThat(stats3.name(), is("a"));
+        assertThat(stats3.type(), is(MapEvent.Type.UPDATE));
+        assertThat(stats3.key(), is("1"));
+        assertThat(stats3.value(), is(vStatsNew));
+        assertThat(stats3.newValue(), is(vStatsNew));
+        assertThat(stats3.oldValue(), is(vStatsOld));
     }
 
     /**