diff --git a/spanner/google/cloud/spanner_v1/pool.py b/spanner/google/cloud/spanner_v1/pool.py
index 8af3e566cab5..ce7a196b6bb8 100644
--- a/spanner/google/cloud/spanner_v1/pool.py
+++ b/spanner/google/cloud/spanner_v1/pool.py
@@ -503,7 +503,7 @@ def put(self, session):
             raise queue.Full
 
         txn = session._transaction
-        if txn is None or txn.committed() or txn._rolled_back:
+        if txn is None or txn.committed or txn._rolled_back:
             session.transaction()
             self._pending_sessions.put(session)
         else:
diff --git a/spanner/tests/unit/test_pool.py b/spanner/tests/unit/test_pool.py
index c5e243e6373c..2d4a9d882291 100644
--- a/spanner/tests/unit/test_pool.py
+++ b/spanner/tests/unit/test_pool.py
@@ -656,7 +656,7 @@ def test_bind(self):
         for session in SESSIONS:
             session.create.assert_not_called()
             txn = session._transaction
-            self.assertTrue(txn._begun)
+            txn.begin.assert_called_once_with()
 
         self.assertTrue(pool._pending_sessions.empty())
 
@@ -685,7 +685,7 @@ def test_bind_w_timestamp_race(self):
         for session in SESSIONS:
             session.create.assert_not_called()
             txn = session._transaction
-            self.assertTrue(txn._begun)
+            txn.begin.assert_called_once_with()
 
         self.assertTrue(pool._pending_sessions.empty())
 
@@ -718,7 +718,7 @@ def test_put_non_full_w_active_txn(self):
         self.assertIs(queued, session)
 
         self.assertEqual(len(pending._items), 0)
-        self.assertFalse(txn._begun)
+        txn.begin.assert_not_called()
 
     def test_put_non_full_w_committed_txn(self):
         pool = self._make_one(size=1)
@@ -727,7 +727,7 @@ def test_put_non_full_w_committed_txn(self):
         database = _Database("name")
         session = _Session(database)
         committed = session.transaction()
-        committed._committed = True
+        committed.committed = True
 
         pool.put(session)
 
@@ -736,7 +736,7 @@ def test_put_non_full_w_committed_txn(self):
         self.assertEqual(len(pending._items), 1)
         self.assertIs(pending._items[0], session)
         self.assertIsNot(session._transaction, committed)
-        self.assertFalse(session._transaction._begun)
+        session._transaction.begin.assert_not_called()
 
     def test_put_non_full(self):
         pool = self._make_one(size=1)
@@ -762,7 +762,7 @@ def test_begin_pending_transactions_non_empty(self):
         pool._sessions = _Queue()
 
         database = _Database("name")
-        TRANSACTIONS = [_Transaction()]
+        TRANSACTIONS = [_make_transaction(object())]
         PENDING_SESSIONS = [_Session(database, transaction=txn) for txn in TRANSACTIONS]
 
         pending = pool._pending_sessions = _Queue(*PENDING_SESSIONS)
@@ -771,7 +771,7 @@ def test_begin_pending_transactions_non_empty(self):
         pool.begin_pending_transactions()  # no raise
 
         for txn in TRANSACTIONS:
-            self.assertTrue(txn._begun)
+            txn.begin.assert_called_once_with()
 
         self.assertTrue(pending.empty())
 
@@ -832,17 +832,13 @@ def test_context_manager_w_kwargs(self):
         self.assertEqual(pool._got, {"foo": "bar"})
 
 
-class _Transaction(object):
+def _make_transaction(*args, **kw):
+    from google.cloud.spanner_v1.transaction import Transaction
 
-    _begun = False
-    _committed = False
-    _rolled_back = False
-
-    def begin(self):
-        self._begun = True
-
-    def committed(self):
-        return self._committed
+    txn = mock.create_autospec(Transaction)(*args, **kw)
+    txn.committed = None
+    txn._rolled_back = False
+    return txn
 
 
 @total_ordering
@@ -873,7 +869,7 @@ def delete(self):
             raise NotFound("unknown session")
 
     def transaction(self):
-        txn = self._transaction = _Transaction()
+        txn = self._transaction = _make_transaction(self)
         return txn