diff -r 290d970c011d Lib/test/test_warnings.py
--- a/Lib/test/test_warnings.py	Wed May 23 23:16:14 2012 +0200
+++ b/Lib/test/test_warnings.py	Wed May 23 14:49:18 2012 -0700
@@ -1,4 +1,5 @@
 from contextlib import contextmanager
+import marshal
 import linecache
 import os
 import StringIO
@@ -706,35 +707,42 @@
 
 class EnvironmentVariableTests(BaseTest):
 
+    def check_child(self, env, cmdline, expected):
+        newenv = os.environ.copy()
+        newenv["PYTHONWARNINGS"] = env
+
+        cmd = [sys.executable]
+        if cmdline:
+            cmd.extend(["-W", cmdline])
+
+        cmd.extend([
+            "-c",
+            "import sys, marshal; marshal.dump(sys.warnoptions, sys.stdout)",
+        ])
+
+        p = subprocess.Popen(cmd, stdout=subprocess.PIPE, env=newenv)
+        self.assertEqual(p.wait(), 0)
+        child_opts = marshal.load(p.stdout)
+        self.assertEqual(set(child_opts), set(expected))
+
     def test_single_warning(self):
-        newenv = os.environ.copy()
-        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
-        p = subprocess.Popen([sys.executable,
-                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
-                stdout=subprocess.PIPE, env=newenv)
-        self.assertEqual(p.communicate()[0], "['ignore::DeprecationWarning']")
-        self.assertEqual(p.wait(), 0)
+        self.check_child(
+            "ignore::DeprecationWarning",
+            None,
+            ["ignore::DeprecationWarning"])
 
     def test_comma_separated_warnings(self):
-        newenv = os.environ.copy()
-        newenv["PYTHONWARNINGS"] = ("ignore::DeprecationWarning,"
-                                    "ignore::UnicodeWarning")
-        p = subprocess.Popen([sys.executable,
-                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
-                stdout=subprocess.PIPE, env=newenv)
-        self.assertEqual(p.communicate()[0],
-                "['ignore::DeprecationWarning', 'ignore::UnicodeWarning']")
-        self.assertEqual(p.wait(), 0)
+        self.check_child(
+            "ignore::DeprecationWarning,ignore::UnicodeWarning",
+            None,
+            ['ignore::DeprecationWarning', 'ignore::UnicodeWarning'])
 
     def test_envvar_and_command_line(self):
-        newenv = os.environ.copy()
-        newenv["PYTHONWARNINGS"] = "ignore::DeprecationWarning"
-        p = subprocess.Popen([sys.executable, "-W" "ignore::UnicodeWarning",
-                "-c", "import sys; sys.stdout.write(str(sys.warnoptions))"],
-                stdout=subprocess.PIPE, env=newenv)
-        self.assertEqual(p.communicate()[0],
-                "['ignore::UnicodeWarning', 'ignore::DeprecationWarning']")
-        self.assertEqual(p.wait(), 0)
+        self.check_child(
+            "ignore::DeprecationWarning",
+            "ignore::UnicodeWarning",
+            ['ignore::UnicodeWarning', 'ignore::DeprecationWarning'])
+
 
 class CEnvironmentVariableTests(EnvironmentVariableTests):
     module = c_warnings
@@ -746,15 +754,21 @@
 def test_main():
     py_warnings.onceregistry.clear()
     c_warnings.onceregistry.clear()
-    test_support.run_unittest(CFilterTests, PyFilterTests,
-                                CWarnTests, PyWarnTests,
-                                CWCmdLineTests, PyWCmdLineTests,
-                                _WarningsTests,
-                                CWarningsDisplayTests, PyWarningsDisplayTests,
-                                CCatchWarningTests, PyCatchWarningTests,
-                                CEnvironmentVariableTests,
-                                PyEnvironmentVariableTests
-                             )
+    test_support.run_unittest(
+        CFilterTests,
+        PyFilterTests,
+        CWarnTests,
+        PyWarnTests,
+        CWCmdLineTests,
+        PyWCmdLineTests,
+        _WarningsTests,
+        CWarningsDisplayTests,
+        PyWarningsDisplayTests,
+        CCatchWarningTests,
+        PyCatchWarningTests,
+        CEnvironmentVariableTests,
+        PyEnvironmentVariableTests
+     )
 
 
 if __name__ == "__main__":