diff -r c3a09c535001 Doc/library/unittest.rst
--- a/Doc/library/unittest.rst	Sat Feb 23 08:40:39 2013 +0200
+++ b/Doc/library/unittest.rst	Sat Feb 23 19:54:02 2013 +0100
@@ -1510,6 +1510,10 @@
 
       *start_dir* can be a dotted module name as well as a directory.
 
+      Paths are sorted before being imported to ensure execution order for a
+      given test suite is the same even if the underlying file system's ordering
+      is not dependent on file name like in ext3/4.
+
       .. versionadded:: 3.2
 
 
diff -r c3a09c535001 Lib/unittest/loader.py
--- a/Lib/unittest/loader.py	Sat Feb 23 08:40:39 2013 +0200
+++ b/Lib/unittest/loader.py	Sat Feb 23 19:54:02 2013 +0100
@@ -169,6 +169,9 @@
         The pattern is deliberately not stored as a loader attribute so that
         packages can continue discovery themselves. top_level_dir is stored so
         load_tests does not need to pass this argument in to loader.discover().
+
+        Paths are sorted before being imported to ensure reproducible execution
+        order even on filesystems with non-alphabetical ordering like ext3/4.
         """
         set_implicit_top = False
         if top_level_dir is None and self._top_level_dir is not None:
@@ -245,7 +248,7 @@
 
     def _find_tests(self, start_dir, pattern):
         """Used by discovery. Yields test suites it loads."""
-        paths = os.listdir(start_dir)
+        paths = sorted(os.listdir(start_dir))
 
         for path in paths:
             full_path = os.path.join(start_dir, path)