@Test
public void testPut() {

   MessageGroups<String> messageGroups = new BucketMessageGroups<>(2);
   assertEquals(0, messageGroups.size());
   messageGroups.put(toGroupBucketIntKey(1), "world");
   assertEquals(1, messageGroups.size());
   messageGroups.put(toGroupBucketIntKey(2), "world2");
   assertEquals(2, messageGroups.size());
   //This as we have 2 buckets, max size will be 2 always
   messageGroups.put(toGroupBucketIntKey(3), "world3");
   assertEquals(2, messageGroups.size());
}