verify getBytesWritten returns correct value after complete

Author: beryllw

fluss-lake/fluss-lake-iceberg/src/test/java/org/apache/fluss/lake/iceberg/tiering/IcebergTieringTest.java

@@ -178,6 +178,8 @@ void testTieringWriteTable(boolean isPrimaryKeyTable, boolean isPartitionedTable
                         writer.write(record);
                     }
                     IcebergWriteResult result = writer.complete();
+                    // Verify that getBytesWritten returns a positive value after complete
+                    assertThat(writer.getBytesWritten()).isGreaterThan(0);
                     byte[] serialized = writeResultSerializer.serialize(result);
                     icebergWriteResults.add(
                             writeResultSerializer.deserialize(

fluss-lake/fluss-lake-lance/src/test/java/org/apache/fluss/lake/lance/tiering/LanceTieringTest.java

@@ -159,6 +159,8 @@ void testTieringWriteTable(boolean isPartitioned) throws Exception {
                     }
                     // serialize/deserialize writeResult
                     LanceWriteResult lanceWriteResult = lakeWriter.complete();
+                    // Verify that getBytesWritten returns a positive value after complete
+                    assertThat(lakeWriter.getBytesWritten()).isEqualTo(-1L);
                     byte[] serialized = writeResultSerializer.serialize(lanceWriteResult);
                     lanceWriteResults.add(
                             writeResultSerializer.deserialize(

fluss-lake/fluss-lake-paimon/src/test/java/org/apache/fluss/lake/paimon/tiering/PaimonTieringTest.java

@@ -957,6 +957,8 @@ private void writeData(
                     }
                     // serialize/deserialize writeResult
                     PaimonWriteResult paimonWriteResult = lakeWriter.complete();
+                    // Verify that getBytesWritten returns a positive value after complete
+                    assertThat(lakeWriter.getBytesWritten()).isGreaterThan(0);
                     byte[] serialized = writeResultSerializer.serialize(paimonWriteResult);
                     paimonWriteResults.add(
                             writeResultSerializer.deserialize(