expect precommit token only when session is multiplexed.

Author: rahul2393

google/cloud/spanner_v1/transaction.py

@@ -289,7 +289,9 @@ def wrapped_method(*args, **kwargs):
                     "mutations": mutations,
                     **common_commit_request_args,
                 }
-                if self._session.is_multiplexed and self._precommit_token is not None:
+                # Check if session is multiplexed (safely handle mock sessions)
+                is_multiplexed = getattr(self._session, "is_multiplexed", False)
+                if is_multiplexed and self._precommit_token is not None:
                     commit_request_args["precommit_token"] = self._precommit_token
 
                 commit_method = functools.partial(

tests/unit/test_transaction.py

@@ -493,11 +493,15 @@ def _commit_helper(
             "request_options": expected_request_options,
         }
 
-        expected_commit_request = CommitRequest(
-            mutations=transaction._mutations,
-            precommit_token=transaction._precommit_token,
+        # Only include precommit_token if the session is multiplexed and token exists
+        commit_request_args = {
+            "mutations": transaction._mutations,
             **common_expected_commit_response_args,
-        )
+        }
+        if session.is_multiplexed and transaction._precommit_token is not None:
+            commit_request_args["precommit_token"] = transaction._precommit_token
+
+        expected_commit_request = CommitRequest(**commit_request_args)
 
         expected_commit_metadata = base_metadata.copy()
         expected_commit_metadata.append(