Adopt MaxBytes test

Signed-off-by: Tomasz Pietrek <tomasz@nats.io>

server/jetstream_test.go

@@ -16808,25 +16808,39 @@ func TestJetStreamPullMaxBytes(t *testing.T) {
 	req = &JSApiConsumerGetNextRequest{Batch: 1, MaxBytes: 10_000_000, NoWait: true}
 	jreq, _ = json.Marshal(req)
 	nc.PublishRequest(subj, reply, jreq)
-	checkSubsPending(t, sub, 1)
+	// we expect two messages, as the second one should be `Batch Completed` status.
+	checkSubsPending(t, sub, 2)
 
+	// first one is message from the stream.
 	m, err = sub.NextMsg(time.Second)
 	require_NoError(t, err)
 	require_True(t, len(m.Data) == dsz)
 	require_True(t, len(m.Header) == 0)
+	// second one is the status.
+	m, err = sub.NextMsg(time.Second)
+	require_NoError(t, err)
+	if v := m.Header.Get("Description"); v != "Batch Completed" {
+		t.Fatalf("Expected Batch Completed, got: %s", v)
+	}
 	checkSubsPending(t, sub, 0)
 
 	// Same but with batch > 1
 	req = &JSApiConsumerGetNextRequest{Batch: 5, MaxBytes: 10_000_000, NoWait: true}
 	jreq, _ = json.Marshal(req)
 	nc.PublishRequest(subj, reply, jreq)
-	checkSubsPending(t, sub, 5)
+	// 6, not 5, as 6th is the status.
+	checkSubsPending(t, sub, 6)
 	for i := 0; i < 5; i++ {
 		m, err = sub.NextMsg(time.Second)
 		require_NoError(t, err)
 		require_True(t, len(m.Data) == dsz)
 		require_True(t, len(m.Header) == 0)
 	}
+	m, err = sub.NextMsg(time.Second)
+	require_NoError(t, err)
+	if v := m.Header.Get("Description"); v != "Batch Completed" {
+		t.Fatalf("Expected Batch Completed, got: %s", v)
+	}
 	checkSubsPending(t, sub, 0)
 
 	// Now ask for large batch but make sure we are limited by batch size.