diff --git a/Lib/unittest/loader.py b/Lib/unittest/loader.py
index a6fb95d..360a41e 100644
--- a/Lib/unittest/loader.py
+++ b/Lib/unittest/loader.py
@@ -173,10 +173,7 @@
 
         if not top_level_dir in sys.path:
             # all test modules must be importable from the top level directory
-            # should we *unconditionally* put the start directory in first
-            # in sys.path to minimise likelihood of conflicts between installed
-            # modules and development versions?
-            sys.path.insert(0, top_level_dir)
+            sys.path.append(top_level_dir)
         self._top_level_dir = top_level_dir
 
         is_not_importable = False
@@ -249,16 +246,6 @@
                     except:
                         yield _make_failed_import_test(name, self.suiteClass)
                     else:
-                        mod_file = os.path.abspath(getattr(module, '__file__', full_path))
-                        realpath = os.path.splitext(mod_file)[0]
-                        fullpath_noext = os.path.splitext(full_path)[0]
-                        if realpath.lower() != fullpath_noext.lower():
-                            module_dir = os.path.dirname(realpath)
-                            mod_name = os.path.splitext(os.path.basename(full_path))[0]
-                            expected_dir = os.path.dirname(full_path)
-                            msg = ("%r module incorrectly imported from %r. Expected %r. "
-                                   "Is this module globally installed?")
-                            raise ImportError(msg % (mod_name, module_dir, expected_dir))
                         yield self.loadTestsFromModule(module)
             elif os.path.isdir(full_path):
                 if not os.path.isfile(os.path.join(full_path, '__init__.py')):
diff --git a/Lib/unittest/test/test_discovery.py b/Lib/unittest/test/test_discovery.py
index e6f8910..de60968 100644
--- a/Lib/unittest/test/test_discovery.py
+++ b/Lib/unittest/test/test_discovery.py
@@ -298,45 +298,6 @@
         self.assertTrue(program.failfast)
         self.assertTrue(program.catchbreak)
 
-    def test_detect_module_clash(self):
-        class Module(object):
-            __file__ = 'bar/foo.py'
-        sys.modules['foo'] = Module
-        full_path = os.path.abspath('foo')
-        original_listdir = os.listdir
-        original_isfile = os.path.isfile
-        original_isdir = os.path.isdir
-
-        def cleanup():
-            os.listdir = original_listdir
-            os.path.isfile = original_isfile
-            os.path.isdir = original_isdir
-            del sys.modules['foo']
-            if full_path in sys.path:
-                sys.path.remove(full_path)
-        self.addCleanup(cleanup)
-
-        def listdir(_):
-            return ['foo.py']
-        def isfile(_):
-            return True
-        def isdir(_):
-            return True
-        os.listdir = listdir
-        os.path.isfile = isfile
-        os.path.isdir = isdir
-
-        loader = unittest.TestLoader()
-
-        mod_dir = os.path.abspath('bar')
-        expected_dir = os.path.abspath('foo')
-        msg = (r"^'foo' module incorrectly imported from %r\. Expected %r\. "
-                "Is this module globally installed\?$") % (mod_dir, expected_dir)
-        self.assertRaisesRegexp(
-            ImportError, msg, loader.discover,
-            start_dir='foo', pattern='foo.py'
-        )
-        self.assertEqual(sys.path[0], full_path)
 
 if __name__ == '__main__':
     unittest.main()