test:

1. Setting isNullValue field will improve the entry size and
2. The default value of isNullValue is set to true will make the break changes for some usages.

Author: liangyepianzhou

pulsar-broker/src/test/java/org/apache/pulsar/broker/admin/PersistentTopicsTest.java

@@ -1095,7 +1095,7 @@ public void testGetBacklogSizeByMessageId() throws Exception {
         completableFuture.get();
         Assert.assertEquals(Optional.ofNullable(
                         admin.topics().getBacklogSizeByMessageId(topicName + "-partition-0", MessageId.earliest)),
-                Optional.of(320L));
+                Optional.of(350L));
     }
 
     @Test

pulsar-broker/src/test/java/org/apache/pulsar/broker/stats/PrometheusMetricsTest.java

@@ -1765,7 +1765,7 @@ public void testCompaction() throws Exception {
         assertEquals(cm.get(0).value, 10);
         cm = (List<Metric>) metrics.get("pulsar_compaction_compacted_entries_size");
         assertEquals(cm.size(), 1);
-        assertEquals(cm.get(0).value, 840);
+        assertEquals(cm.get(0).value, 870);
 
         pulsarClient.close();
     }

pulsar-broker/src/test/java/org/apache/pulsar/compaction/CompactionTest.java

@@ -1384,7 +1384,7 @@ public void testEmptyPayloadDeletesWhenEncrypted() throws Exception {
 
                 Message<byte[]> message4 = consumer.receive();
                 Assert.assertEquals(message4.getKey(), "key2");
-                Assert.assertEquals(new String(message4.getData()), "");
+                assertNull(message4.getData());
 
                 Message<byte[]> message5 = consumer.receive();
                 Assert.assertEquals(message5.getKey(), "key4");