Add test_main() methods. These three tests were never run
by regrtest.py.

We really need a simpler testing framework.
diff --git a/Lib/test/test_defaultdict.py b/Lib/test/test_defaultdict.py
index b5a6628..134b5a8 100644
--- a/Lib/test/test_defaultdict.py
+++ b/Lib/test/test_defaultdict.py
@@ -4,6 +4,7 @@
 import copy
 import tempfile
 import unittest
+from test import test_support
 
 from collections import defaultdict
 
@@ -131,5 +132,8 @@
         self.assertEqual(d2, d1)
 
 
+def test_main():
+    test_support.run_unittest(TestDefaultDict)
+
 if __name__ == "__main__":
-    unittest.main()
+    test_main()