test: adjust version time to avoid future timestamp error (#538)

* test: adjust version time to avoid future timestamp error

* 🦉 Updates from OwlBot

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* fix: use None when encryption config is empty

Co-authored-by: larkee <larkee@users.noreply.github.com>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

google/cloud/spanner_v1/database.py

@@ -694,7 +694,7 @@ def restore(self, source):
             parent=self._instance.name,
             database_id=self.database_id,
             backup=source.name,
-            encryption_config=self._encryption_config,
+            encryption_config=self._encryption_config or None,
         )
         future = api.restore_database(request=request, metadata=metadata,)
         return future

tests/system/test_backup_api.py

@@ -79,9 +79,14 @@ def diff_config_instance(
     _helpers.scrub_instance_ignore_not_found(diff_config_instance)
 
 
-@pytest.fixture(scope="function")
-def database_version_time(shared_database):  # Ensure database exists.
-    return datetime.datetime.now(datetime.timezone.utc)
+@pytest.fixture(scope="session")
+def database_version_time(shared_database):
+    shared_database.reload()
+    diff = (
+        datetime.datetime.now(datetime.timezone.utc)
+        - shared_database.earliest_version_time
+    )
+    return shared_database.earliest_version_time + diff / 2
 
 
 @pytest.fixture(scope="session")