cache is always a dictionary in memory

test/test_storage.py

@@ -6,7 +6,9 @@ from tiramisu.config import Config
 from tiramisu.option import BoolOption, OptionDescription
 from tiramisu.setting import owners
 from tiramisu.storage import list_sessions, delete_session
+from tiramisu import setting
 
+setting.expires_time = 0
 
 def test_non_persistent():
     b = BoolOption('b', '')