Modify existing test to verify code change behaviour

Signed-off-by: Ashish Singh <ssashish@amazon.com>

Author: ashking94

server/src/test/java/org/opensearch/indices/replication/SegmentReplicationTargetServiceTests.java

@@ -625,6 +625,7 @@ public void testStartReplicationListenerSuccess() throws InterruptedException {
 
         latch.await(2, TimeUnit.SECONDS);
         verify(spy, (atLeastOnce())).updateVisibleCheckpoint(eq(0L), eq(replicaShard));
+        verify(spy, times(1)).processLatestReceivedCheckpoint(any(), any());
     }
 
     public void testStartReplicationListenerFailure() throws InterruptedException {
@@ -851,4 +852,5 @@ public void testProcessCheckpointOnClusterStateUpdate() {
         spy.clusterChanged(new ClusterChangedEvent("ignored", oldState, newState));
         verify(spy, times(1)).processLatestReceivedCheckpoint(eq(replicaShard), any());
     }
+
 }