Make run_in_transaction w/ timeout test deterministic.

spanner/unit_tests/test_session.py

@@ -749,6 +749,8 @@ def unit_of_work(txn, *args, **kw):
         self.assertEqual(kw, {'some_arg': 'def'})
 
     def test_run_in_transaction_w_timeout(self):
+        from google.cloud.spanner import session as MUT
+        from google.cloud._testing import _Monkey
         from google.gax.errors import GaxError
         from google.gax.grpc import exc_to_code
         from google.cloud.proto.spanner.v1.transaction_pb2 import (
@@ -779,12 +781,17 @@ def unit_of_work(txn, *args, **kw):
             called_with.append((txn, args, kw))
             txn.insert(TABLE_NAME, COLUMNS, VALUES)
 
-        with self.assertRaises(GaxError) as exc:
-            session.run_in_transaction(unit_of_work, timeout_secs=0.01)
+        time_module = _FauxTimeModule()
+        time_module._times = [1, 1.5, 2.5]  # retry once w/ timeout_secs=1
+
+        with _Monkey(MUT, time=time_module):
+            with self.assertRaises(GaxError) as exc:
+                session.run_in_transaction(unit_of_work, timeout_secs=1)
 
         self.assertEqual(exc_to_code(exc.exception.cause), StatusCode.ABORTED)
 
-        self.assertGreater(len(called_with), 1)
+        self.assertEqual(time_module._slept, None)
+        self.assertEqual(len(called_with), 2)
         for txn, args, kw in called_with:
             self.assertIsInstance(txn, Transaction)
             self.assertIsNone(txn.committed)
@@ -881,9 +888,14 @@ def __init__(self, name):
 class _FauxTimeModule(object):
 
     _slept = None
+    _times = ()
 
     def time(self):
         import time
+
+        if len(self._times) > 0:
+            return self._times.pop(0)
+
         return time.time()
 
     def sleep(self, seconds):