ONOS-4018 - Enhance the DistributedRegionStore to make sure that a
device ID appears in at most one Region's list of devices.

Change-Id: I6d30fab2c09544c68f49b11682f08ee8ded060fe
diff --git a/core/store/dist/src/test/java/org/onosproject/store/region/impl/DistributedRegionStoreTest.java b/core/store/dist/src/test/java/org/onosproject/store/region/impl/DistributedRegionStoreTest.java
index df3f048..5612e38 100644
--- a/core/store/dist/src/test/java/org/onosproject/store/region/impl/DistributedRegionStoreTest.java
+++ b/core/store/dist/src/test/java/org/onosproject/store/region/impl/DistributedRegionStoreTest.java
@@ -137,6 +137,15 @@
         deviceIds = store.getRegionDevices(RID1);
         assertEquals("incorrect device count", 3, deviceIds.size());
 
+        // Test adding DID3 to RID2 but it is already in RID1.
+        // DID3 will be removed from RID1 and added to RID2.
+        Region r2 = store.createRegion(RID2, "R2", CAMPUS, MASTERS);
+        store.addDevices(RID2, ImmutableSet.of(DID3));
+        deviceIds = store.getRegionDevices(RID1);
+        assertEquals("incorrect device count", 2, deviceIds.size());
+        deviceIds = store.getRegionDevices(RID2);
+        assertEquals("incorrect device count", 1, deviceIds.size());
+
         store.removeDevices(RID1, ImmutableSet.of(DID2, DID3));
         deviceIds = store.getRegionDevices(RID1);
         assertEquals("incorrect device count", 1, deviceIds.size());