feat: Multiplexed sessions - Add unit tests for begin transaction base class, simplify _SnapshotBase tests, remove redundant tests.

Signed-off-by: Taylor Curran <taylor.curran@improving.com>

Author: currantw

tests/_builders.py

@@ -25,9 +25,12 @@
 from google.cloud.spanner_v1.session import Session
 from google.cloud.spanner_v1.transaction import Transaction
 
-from google.cloud.spanner_v1.types import Session as SessionPB
-from google.cloud.spanner_v1.types import Transaction as TransactionPB
-from google.cloud.spanner_v1.types import CommitResponse as CommitResponsePB
+from google.cloud.spanner_v1.types import (
+    CommitResponse as CommitResponsePB,
+    MultiplexedSessionPrecommitToken as PrecommitTokenPB,
+    Session as SessionPB,
+    Transaction as TransactionPB,
+)
 
 from google.cloud._helpers import _datetime_to_pb_timestamp
 from tests._helpers import HAS_OPENTELEMETRY_INSTALLED, get_test_ot_exporter
@@ -39,20 +42,22 @@
 _INSTANCE_ID = "default-instance-id"
 _DATABASE_ID = "default-database-id"
 _SESSION_ID = "default-session-id"
-_TRANSACTION_ID = b"default-transaction-id"
 
 _PROJECT_NAME = "projects/" + _PROJECT_ID
 _INSTANCE_NAME = _PROJECT_NAME + "/instances/" + _INSTANCE_ID
 _DATABASE_NAME = _INSTANCE_NAME + "/databases/" + _DATABASE_ID
 _SESSION_NAME = _DATABASE_NAME + "/sessions/" + _SESSION_ID
 
+_TRANSACTION_ID = b"default-transaction-id"
+_PRECOMMIT_TOKEN = b"default-precommit-token"
+_SEQUENCE_NUMBER = -1
 _TIMESTAMP = _datetime_to_pb_timestamp(datetime.now())
 
 # Protocol buffers
 # ----------------
 
 
-def _build_commit_response_pb(**kwargs) -> CommitResponsePB:
+def build_commit_response_pb(**kwargs) -> CommitResponsePB:
     """Builds and returns a commit response protocol buffer for testing using the given arguments.
     If an expected argument is not provided, a default value will be used."""
 
@@ -62,6 +67,20 @@ def _build_commit_response_pb(**kwargs) -> CommitResponsePB:
     return CommitResponsePB(**kwargs)
 
 
+def build_precommit_token_pb(**kwargs) -> PrecommitTokenPB:
+    """Builds and returns a multiplexed session precommit token protocol buffer for
+    testing using the given arguments. If an expected argument is not provided, a
+    default value will be used."""
+
+    if "precommit_token" not in kwargs:
+        kwargs["precommit_token"] = _PRECOMMIT_TOKEN
+
+    if "seq_num" not in kwargs:
+        kwargs["seq_num"] = _SEQUENCE_NUMBER
+
+    return PrecommitTokenPB(**kwargs)
+
+
 def build_session_pb(**kwargs) -> SessionPB:
     """Builds and returns a session protocol buffer for testing using the given arguments.
     If an expected argument is not provided, a default value will be used."""
@@ -195,7 +214,7 @@ def build_spanner_api() -> SpannerClient:
 
     # Mock API calls with default return values.
     api.begin_transaction.return_value = build_transaction_pb()
-    api.commit.return_value = _build_commit_response_pb()
+    api.commit.return_value = build_commit_response_pb()
     api.create_session.return_value = build_session_pb()
 
     return api