diff -r 3c34ab550358 Lib/threading.py
--- a/Lib/threading.py	Wed Dec 04 01:47:46 2013 +0100
+++ b/Lib/threading.py	Wed Dec 04 02:02:18 2013 +0100
@@ -16,6 +16,8 @@ try:
 except ImportError:
     from collections import deque as _deque
 
+import tracemalloc
+
 # Note regarding PEP 8 compliant names
 #  This threading model was originally inspired by Java, and inherited
 # the convention of camelCase function and method names from that
@@ -848,6 +850,7 @@ class Thread:
         with _active_limbo_lock:
             _limbo[self] = self
         try:
+            tracemalloc.stop()
             _start_new_thread(self._bootstrap, ())
         except Exception:
             with _active_limbo_lock:
@@ -885,6 +888,7 @@ class Thread:
         # _bootstrap_inner() during normal business hours are properly
         # reported.  Also, we only suppress them for daemonic threads;
         # if a non-daemonic encounters this, something else is wrong.
+        tracemalloc.stop()
         try:
             self._bootstrap_inner()
         except:
diff -r 3c34ab550358 Lib/unittest/case.py
--- a/Lib/unittest/case.py	Wed Dec 04 01:47:46 2013 +0100
+++ b/Lib/unittest/case.py	Wed Dec 04 02:02:18 2013 +0100
@@ -9,6 +9,8 @@ import re
 import warnings
 import collections
 import contextlib
+import tracemalloc
+import random
 
 from . import result
 from .util import (strclass, safe_repr, _count_diff_all_purpose,
@@ -567,8 +569,13 @@ class TestCase(object):
                 self.setUp()
             if outcome.success:
                 outcome.expecting_failure = expecting_failure
+                limit = random.randint(100, 1024*50)
                 with outcome.testPartExecutor(self, isTest=True):
-                    testMethod()
+                    tracemalloc.start(memory_limit=limit)
+                    try:
+                        testMethod()
+                    finally:
+                        tracemalloc.stop()
                 outcome.expecting_failure = False
                 with outcome.testPartExecutor(self):
                     self.tearDown()