Use None instead of mutables in test method params defaults

Mutables in the method params defaults might cause errors and
that's why it's anti-pattern in most of the cases and should be
removed.

Change-Id: Ie9897aae6e95962e0991ac9d9fc5c175f2da12a4

ceilometer/tests/alarm/partition/test_coordination.py

@@ -154,11 +154,11 @@ class TestCoordinate(tests_base.BaseTestCase):
         return (pid, younger)
 
     def _check_assignments(self, others, alarm_ids, per_worker,
-                           expect_uneffected=[]):
+                           expect_uneffected=None):
         rpc = self.partition_coordinator.coordination_rpc
         calls = rpc.assign.call_args_list
         return self._check_distribution(others, alarm_ids, per_worker, calls,
-                                        expect_uneffected)
+                                        expect_uneffected or [])
 
     def _check_allocation(self, others, alarm_ids, per_worker):
         rpc = self.partition_coordinator.coordination_rpc
@@ -166,7 +166,8 @@ class TestCoordinate(tests_base.BaseTestCase):
         return self._check_distribution(others, alarm_ids, per_worker, calls)
 
     def _check_distribution(self, others, alarm_ids, per_worker, calls,
-                            expect_uneffected=[]):
+                            expect_uneffected=None):
+        expect_uneffected = expect_uneffected or []
         uneffected = [pid for pid, _ in others]
         uneffected.extend(expect_uneffected)
         remainder = list(alarm_ids)

ceilometer/tests/api/v2/test_alarm_scenarios.py

@@ -1294,12 +1294,12 @@ class TestAlarms(v2.FunctionalTest,
                          alarms[0].rule.get('alarm_ids'))
 
     def _test_post_alarm_combination_rule_less_than_two_alarms(self,
-                                                               alarm_ids=[]):
+                                                               alarm_ids=None):
         json_body = {
             'name': 'one_alarm_in_combination_rule',
             'type': 'combination',
             'combination_rule': {
-                'alarm_ids': alarm_ids
+                'alarm_ids': alarm_ids or []
             }
         }
 
@@ -1511,12 +1511,12 @@ class TestAlarms(v2.FunctionalTest,
         self.assertEqual(msg, resp.json['error_message']['faultstring'])
 
     def _test_put_alarm_combination_rule_less_than_two_alarms(self,
-                                                              alarm_ids=[]):
+                                                              alarm_ids=None):
         json_body = {
             'name': 'name4',
             'type': 'combination',
             'combination_rule': {
-                'alarm_ids': alarm_ids
+                'alarm_ids': alarm_ids or []
             }
         }
 

ceilometer/tests/objectstore/test_swift_middleware.py

@@ -35,8 +35,9 @@ from ceilometer.tests import base as tests_base
 
 
 class FakeApp(object):
-    def __init__(self, body=['This string is 28 bytes long']):
-        self.body = body
+    def __init__(self, body=None):
+
+        self.body = body or ['This string is 28 bytes long']
 
     def __call__(self, env, start_response):
         yield

ceilometer/tests/storage/test_storage_scenarios.py

@@ -35,14 +35,14 @@ from ceilometer.tests import db as tests_db
 
 class DBTestBase(tests_db.TestBase):
     def create_and_store_sample(self, timestamp=datetime.datetime.utcnow(),
-                                metadata={
-                                    'display_name': 'test-server',
-                                    'tag': 'self.counter'},
+                                metadata=None,
                                 name='instance',
                                 sample_type=sample.TYPE_CUMULATIVE, unit='',
                                 volume=1, user_id='user-id',
                                 project_id='project-id',
                                 resource_id='resource-id', source=None):
+        metadata = metadata or {'display_name': 'test-server',
+                                'tag': 'self.counter'}
         s = sample.Sample(
             name, sample_type, unit=unit, volume=volume, user_id=user_id,
             project_id=project_id, resource_id=resource_id,