make refcount tests more consistent

tests/__init__.py

@@ -1,6 +1,8 @@
 """Tests. They want YOU!!"""
-
 from __future__ import print_function
+
+import gc
+import sys
 import unittest
 import pylibmc
 from pylibmc.test import make_test_client
@@ -29,3 +31,13 @@ def dump_infos():
     print("Reported libmemcached version:", _pylibmc.libmemcached_version)
     print("Reported pylibmc version:", _pylibmc.__version__)
     print("Support compression:", _pylibmc.support_compression)
+
+def get_refcounts(refcountables):
+    """Measure reference counts during testing.
+
+    Measuring reference counts typically changes them (since at least
+    one new reference is created as the argument to sys.getrefcount).
+    Therefore, try to do it in a consistent and deterministic fashion.
+    """
+    gc.collect()
+    return [sys.getrefcount(val) for val in refcountables]

tests/test_refcounts.py

@@ -10,10 +10,7 @@
 import _pylibmc
 from pylibmc.test import make_test_client
 from tests import PylibmcTestCase
-
-
-def get_refcounts(refcountables):
-    return [sys.getrefcount(val) for val in refcountables]
+from tests import get_refcounts
 
 
 class RefcountTests(PylibmcTestCase):

tests/test_serialization.py

@@ -10,10 +10,7 @@
 import _pylibmc
 from pylibmc.test import make_test_client
 from tests import PylibmcTestCase
-
-
-def get_refcounts(refcountables):
-    return [sys.getrefcount(val) for val in refcountables]
+from tests import get_refcounts
 
 def long_(val):
     try:
@@ -47,7 +44,7 @@ def __setstate__(self, d):
         c = make_test_client(MyClient, behaviors={'cas': True})
         eq_(c.get('notathing'), None)
 
-        refcountables = ['foo', 'myobj', 'noneobj', 'myobj2', 'cachemiss', None]
+        refcountables = ['foo', 'myobj', 'noneobj', 'myobj2', 'cachemiss']
         initial_refcounts = get_refcounts(refcountables)
 
         c['foo'] = 'foo'