Using this patch, I can see the list of "python" processes slowly growing:

diff -r ad5b079565ad Lib/unittest/case.py
--- a/Lib/unittest/case.py      Tue Apr 12 23:15:44 2016 -0700
+++ b/Lib/unittest/case.py      Fri Apr 15 11:06:07 2016 +0200
@@ -10,6 +10,7 @@ import warnings
 import collections
 import contextlib
 import traceback
+import os
 
 from . import result
 from .util import (strclass, safe_repr, _count_diff_all_purpose,
@@ -590,6 +591,7 @@ class TestCase(object):
         expecting_failure = expecting_failure_class or expecting_failure_method
         outcome = _Outcome(result)
         try:
+            os.system("ps")
             self._outcome = outcome
 
             with outcome.testPartExecutor(self):
@@ -614,6 +616,7 @@ class TestCase(object):
                         self._addUnexpectedSuccess(result)
                 else:
                     result.addSuccess(self)
+            os.system("ps")
             return result
         finally:
             result.stopTest(self)