diff --git a/IPython/testing/iptest.py b/IPython/testing/iptest.py
index 0a99b99..9e4f74b 100644
--- a/IPython/testing/iptest.py
+++ b/IPython/testing/iptest.py
@@ -1,15 +1,53 @@
 # -*- coding: utf-8 -*-
 """IPython Test Suite Runner.
+
+This module provides a main entry point to a user script to test IPython itself
+from the command line.  The main() routine can be used in a similar manner to
+the ``nosetests`` script, and it takes similar arguments, but if no arguments
+are given it defaults to testing all of IPython.  This should be preferred to
+using plain ``nosetests`` because a number of nose plugins necessary to test
+IPython correctly are automatically configured by this code.
 """
 
+#-----------------------------------------------------------------------------
+# Module imports
+#-----------------------------------------------------------------------------
+
+# stdlib
 import sys
 import warnings
 
-from nose.core import TestProgram
+# third-party
 import nose.plugins.builtin
+from nose.core import TestProgram
 
+# Our own imports
 from IPython.testing.plugin.ipdoctest import IPythonDoctest
 
+#-----------------------------------------------------------------------------
+# Constants and globals
+#-----------------------------------------------------------------------------
+
+# For the IPythonDoctest plugin, we need to exclude certain patterns that cause
+# testing problems.  We should strive to minimize the number of skipped
+# modules, since this means untested code.  As the testing machinery
+# solidifies, this list should eventually become empty.
+EXCLUDE = ['IPython/external/',
+           'IPython/platutils_win32',
+           'IPython/frontend/cocoa',
+           'IPython_doctest_plugin',
+           'IPython/Gnuplot',
+           'IPython/Extensions/ipy_',
+           'IPython/Extensions/clearcmd',
+           'IPython/Extensions/PhysicalQIn',
+           'IPython/Extensions/scitedirector',
+           'IPython/testing/plugin',
+           ]
+
+#-----------------------------------------------------------------------------
+# Functions and classes
+#-----------------------------------------------------------------------------
+
 def main():
     """Run the IPython test suite.
     """
@@ -42,8 +80,8 @@ def main():
     if not has_tests:
         argv.append('IPython')
 
-    # construct list of plugins, omitting the existing doctest plugin
-    plugins = [IPythonDoctest()]
+    # Construct list of plugins, omitting the existing doctest plugin.
+    plugins = [IPythonDoctest(EXCLUDE)]
     for p in nose.plugins.builtin.plugins:
         plug = p()
         if plug.name == 'doctest':
diff --git a/IPython/testing/plugin/ipdoctest.py b/IPython/testing/plugin/ipdoctest.py
index 59cb945..577386c 100644
--- a/IPython/testing/plugin/ipdoctest.py
+++ b/IPython/testing/plugin/ipdoctest.py
@@ -677,6 +677,22 @@ class ExtensionDoctest(doctests.Doctest):
     name = 'extdoctest'   # call nosetests with --with-extdoctest
     enabled = True
 
+    def __init__(self,exclude_patterns=None):
+        """Create a new ExtensionDoctest plugin.
+
+        Parameters
+        ----------
+
+        exclude_patterns : sequence of strings, optional
+          These patterns are compiled as regular expressions, subsequently used
+          to exclude any filename which matches them from inclusion in the test
+          suite (using pattern.search(), NOT pattern.match() ).
+        """
+        if exclude_patterns is None:
+            exclude_patterns = []
+        self.exclude_patterns = map(re.compile,exclude_patterns)
+        doctests.Doctest.__init__(self)
+
     def options(self, parser, env=os.environ):
         Plugin.options(self, parser, env)
         parser.add_option('--doctest-tests', action='store_true',
@@ -783,20 +799,8 @@ class ExtensionDoctest(doctests.Doctest):
         """
         #print '*** ipdoctest- wantFile:',filename  # dbg
 
-        # XXX - temporarily hardcoded list, will move to driver later
-        exclude = ['IPython/external/',
-                   'IPython/platutils_win32',
-                   'IPython/frontend/cocoa',
-                   'IPython_doctest_plugin',
-                   'IPython/Gnuplot',
-                   'IPython/Extensions/ipy_',
-                   'IPython/Extensions/PhysicalQIn',
-                   'IPython/Extensions/scitedirector',
-                   'IPython/testing/plugin',
-                   ]
-
-        for fex in exclude:
-            if fex in filename:  # substring
+        for pat in self.exclude_patterns:
+            if pat.search(filename):
                 #print '###>>> SKIP:',filename  # dbg
                 return False
 
diff --git a/IPython/tests/tclass.py b/IPython/tests/tclass.py
new file mode 100644
index 0000000..9b62fde
--- /dev/null
+++ b/IPython/tests/tclass.py
@@ -0,0 +1,6 @@
+"""Simple script to instantiate a class for testing %run"""
+
+class foo: pass
+
+def f():
+    foo()