--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/parts/django/tests/regressiontests/utils/module_loading.py	Sat Jan 08 11:20:57 2011 +0530
@@ -0,0 +1,114 @@
+import os
+import sys
+import unittest
+from zipimport import zipimporter
+
+from django.utils.importlib import import_module
+from django.utils.module_loading import module_has_submodule
+
+class DefaultLoader(unittest.TestCase):
+    def test_loader(self):
+        "Normal module existence can be tested"
+        test_module = import_module('regressiontests.utils.test_module')
+
+        # An importable child
+        self.assertTrue(module_has_submodule(test_module, 'good_module'))
+        mod = import_module('regressiontests.utils.test_module.good_module')
+        self.assertEqual(mod.content, 'Good Module')
+
+        # A child that exists, but will generate an import error if loaded
+        self.assertTrue(module_has_submodule(test_module, 'bad_module'))
+        self.assertRaises(ImportError, import_module, 'regressiontests.utils.test_module.bad_module')
+
+        # A child that doesn't exist
+        self.assertFalse(module_has_submodule(test_module, 'no_such_module'))
+        self.assertRaises(ImportError, import_module, 'regressiontests.utils.test_module.no_such_module')
+
+class EggLoader(unittest.TestCase):
+    def setUp(self):
+        self.old_path = sys.path[:]
+        self.egg_dir = '%s/eggs' % os.path.dirname(__file__)
+
+    def tearDown(self):
+        sys.path = self.old_path
+        sys.path_importer_cache.clear()
+
+        sys.modules.pop('egg_module.sub1.sub2.bad_module', None)
+        sys.modules.pop('egg_module.sub1.sub2.good_module', None)
+        sys.modules.pop('egg_module.sub1.sub2', None)
+        sys.modules.pop('egg_module.sub1', None)
+        sys.modules.pop('egg_module.bad_module', None)
+        sys.modules.pop('egg_module.good_module', None)
+        sys.modules.pop('egg_module', None)
+
+    def test_shallow_loader(self):
+        "Module existence can be tested inside eggs"
+        egg_name = '%s/test_egg.egg' % self.egg_dir
+        sys.path.append(egg_name)
+        egg_module = import_module('egg_module')
+
+        # An importable child
+        self.assertTrue(module_has_submodule(egg_module, 'good_module'))
+        mod = import_module('egg_module.good_module')
+        self.assertEqual(mod.content, 'Good Module')
+
+        # A child that exists, but will generate an import error if loaded
+        self.assertTrue(module_has_submodule(egg_module, 'bad_module'))
+        self.assertRaises(ImportError, import_module, 'egg_module.bad_module')
+
+        # A child that doesn't exist
+        self.assertFalse(module_has_submodule(egg_module, 'no_such_module'))
+        self.assertRaises(ImportError, import_module, 'egg_module.no_such_module')
+
+    def test_deep_loader(self):
+        "Modules deep inside an egg can still be tested for existence"
+        egg_name = '%s/test_egg.egg' % self.egg_dir
+        sys.path.append(egg_name)
+        egg_module = import_module('egg_module.sub1.sub2')
+
+        # An importable child
+        self.assertTrue(module_has_submodule(egg_module, 'good_module'))
+        mod = import_module('egg_module.sub1.sub2.good_module')
+        self.assertEqual(mod.content, 'Deep Good Module')
+
+        # A child that exists, but will generate an import error if loaded
+        self.assertTrue(module_has_submodule(egg_module, 'bad_module'))
+        self.assertRaises(ImportError, import_module, 'egg_module.sub1.sub2.bad_module')
+
+        # A child that doesn't exist
+        self.assertFalse(module_has_submodule(egg_module, 'no_such_module'))
+        self.assertRaises(ImportError, import_module, 'egg_module.sub1.sub2.no_such_module')
+
+class TestFinder(object):
+    def __init__(self, *args, **kwargs):
+        self.importer = zipimporter(*args, **kwargs)
+
+    def find_module(self, path):
+        importer = self.importer.find_module(path)
+        if importer is None:
+            return
+        return TestLoader(importer)
+
+class TestLoader(object):
+    def __init__(self, importer):
+        self.importer = importer
+
+    def load_module(self, name):
+        mod = self.importer.load_module(name)
+        mod.__loader__ = self
+        return mod
+
+class CustomLoader(EggLoader):
+    """The Custom Loader test is exactly the same as the EggLoader, but
+    it uses a custom defined Loader and Finder that is intentionally
+    split into two classes. Although the EggLoader combines both functions
+    into one class, this isn't required.
+    """
+    def setUp(self):
+        super(CustomLoader, self).setUp()
+        sys.path_hooks.insert(0, TestFinder)
+        sys.path_importer_cache.clear()
+
+    def tearDown(self):
+        super(CustomLoader, self).tearDown()
+        sys.path_hooks.pop(0)