add tests

Signed-off-by: guojialiang <guojialiang.2012@bytedance.com>

Author: guojialiang92

server/src/test/java/org/opensearch/index/shard/SegmentReplicationIndexShardTests.java

@@ -146,6 +146,7 @@ public void testReplication() throws Exception {
 
             // Assertions
             shards.assertAllEqual(numDocs);
+            assertTrue(primaryShard.getReplicationEngine().isEmpty());
             assertFalse(replicaShard.getReplicationEngine().isEmpty());
             replicaShard.close("test", false, false);
             assertTrue(replicaShard.getReplicationEngine().isEmpty());