chore: add test for validating changes

Signed-off-by: Manish Dait <daitmanish88@gmail.com>

Author: manishdait

tests/unit/file_append_transaction_test.py

@@ -4,12 +4,14 @@
 
 import pytest
 
+from hiero_sdk_python.account.account_id import AccountId
 from hiero_sdk_python.exceptions import PrecheckError, ReceiptStatusError
 from hiero_sdk_python.file.file_append_transaction import FileAppendTransaction
 from hiero_sdk_python.file.file_id import FileId
 from hiero_sdk_python.hapi.services import (
     response_header_pb2,
     response_pb2,
+    timestamp_pb2,
     transaction_get_receipt_pb2,
     transaction_receipt_pb2,
     transaction_response_pb2,
@@ -372,3 +374,30 @@ def test_file_append_execute_all_returns_receipt_without_validation(file_id):
         receipts = tx.execute_all(client)
 
         assert receipts[0].status == ResponseCode.INVALID_FILE_ID
+
+
+def test_chunk_transaction_id_nanosecond_overflow(file_id):
+    """Test that multi-chunk transaction IDs handle nanosecond overflow correctly."""
+    base_seconds = 1770911831
+    base_nanos = 999_999_999
+
+    start_timestamp = timestamp_pb2.Timestamp(seconds=base_seconds, nanos=base_nanos)
+    tx_id = TransactionId(account_id=AccountId(0, 0, 2), valid_start=start_timestamp)
+
+    tx = (
+        FileAppendTransaction()
+        .set_file_id(file_id)
+        .set_contents("a" * 20)
+        .set_chunk_size(10)
+        .set_transaction_id(tx_id)
+        .set_node_account_id(AccountId(0, 0, 3))
+        .freeze()
+    )
+
+    # First chunk is exactly equal initial ID
+    assert tx._transaction_ids[0].valid_start.seconds == base_seconds
+    assert tx._transaction_ids[0].valid_start.nanos == base_nanos
+
+    # Second chunk seconds=base_seconds + 1, nanos=0
+    assert tx._transaction_ids[1].valid_start.seconds == base_seconds + 1
+    assert tx._transaction_ids[1].valid_start.nanos == 0

tests/unit/topic_message_submit_transaction_test.py

@@ -6,11 +6,13 @@
 
 import pytest
 
+from hiero_sdk_python.account.account_id import AccountId
 from hiero_sdk_python.consensus.topic_message_submit_transaction import TopicMessageSubmitTransaction
 from hiero_sdk_python.exceptions import PrecheckError, ReceiptStatusError
 from hiero_sdk_python.hapi.services import (
     response_header_pb2,
     response_pb2,
+    timestamp_pb2,
     transaction_get_receipt_pb2,
     transaction_receipt_pb2,
     transaction_response_pb2,
@@ -20,6 +22,7 @@
 )
 from hiero_sdk_python.response_code import ResponseCode
 from hiero_sdk_python.transaction.custom_fee_limit import CustomFeeLimit
+from hiero_sdk_python.transaction.transaction_id import TransactionId
 from hiero_sdk_python.transaction.transaction_receipt import TransactionReceipt
 from hiero_sdk_python.transaction.transaction_response import TransactionResponse
 from tests.unit.mock_server import mock_hedera_servers
@@ -511,3 +514,30 @@ def test_topic_submit_message_raises_error_on_freeze(topic_id):
 
     with pytest.raises(ValueError):
         tx.freeze()
+
+
+def test_chunk_transaction_id_nanosecond_overflow(topic_id):
+    """Test that multi-chunk transaction IDs handle nanosecond overflow correctly."""
+    base_seconds = 1770911831
+    base_nanos = 999_999_999
+
+    start_timestamp = timestamp_pb2.Timestamp(seconds=base_seconds, nanos=base_nanos)
+    tx_id = TransactionId(account_id=AccountId(0, 0, 2), valid_start=start_timestamp)
+
+    tx = (
+        TopicMessageSubmitTransaction()
+        .set_topic_id(topic_id)
+        .set_message("a" * 20)
+        .set_chunk_size(10)
+        .set_transaction_id(tx_id)
+        .set_node_account_id(AccountId(0, 0, 3))
+        .freeze()
+    )
+
+    # First chunk is exactly equal initial ID
+    assert tx._transaction_ids[0].valid_start.seconds == base_seconds
+    assert tx._transaction_ids[0].valid_start.nanos == base_nanos
+
+    # Second chunk seconds=base_seconds + 1, nanos=0
+    assert tx._transaction_ids[1].valid_start.seconds == base_seconds + 1
+    assert tx._transaction_ids[1].valid_start.nanos == 0

tests/unit/transaction_test.py

@@ -355,6 +355,7 @@ def test_message_submit_chunk_tx_should_return_list_of_body_sizes(topic_id, acco
     sizes = tx.body_size_all_chunks
     assert isinstance(sizes, list)
     assert len(sizes) == 3
+    assert tx._current_index == 0
 
 
 def test_message_submit_single_chunk_tx_return_list_of_len_one(topic_id, account_id, transaction_id):
@@ -420,9 +421,27 @@ def test_chunked_tx_return_proper_sizes(file_id, account_id, transaction_id):
 
     # Size should be greater than single chunk size
     assert large_size > 1024
-
     # The larger chunked transaction should be bigger than the single-chunk transaction
     assert large_size > small_size
-
-    # Check for chuck index reset reset
     assert large_tx._current_chunk_index == 0
+
+
+def test_chunked_tx_differ_size_if_chunk_are_not_equal(topic_id, account_id, transaction_id):
+    """Test that the last chunk's size is different from the full chunks if the chunk size is not even."""
+    chunk_size = 1024
+    message = "a" * (chunk_size + 512)
+
+    tx = (
+        TopicMessageSubmitTransaction()
+        .set_topic_id(topic_id)
+        .set_chunk_size(chunk_size)
+        .set_message(message)
+        .set_transaction_id(transaction_id)
+        .set_node_account_id(account_id)
+        .freeze()
+    )
+
+    sizes = tx.body_size_all_chunks
+    assert len(sizes) == 2
+    # The first chunk should be larger than the second because it carries more message data
+    assert sizes[0] > sizes[1]