SF bug 478425:  Change in os.path.join (ntpath.py)
ntpath.join('a', '') was producing 'a' instead of 'a\\' as in 2.1.
Impossible to guess what was ever *intended*, but since split('a\\')
produces ('a', ''), I think it's best if join('a', '') gives 'a\\' back.
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 049bbc1..98569f9 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -74,6 +74,14 @@
 tester("ntpath.join('c:/', 'd:/')", 'd:/')
 tester("ntpath.join('c:/', 'd:/a/b')", 'd:/a/b')
 
+tester("ntpath.join('')", '')
+tester("ntpath.join('', '', '', '', '')", '')
+tester("ntpath.join('a')", 'a')
+tester("ntpath.join('', 'a')", 'a')
+tester("ntpath.join('', '', '', '', 'a')", 'a')
+tester("ntpath.join('a', '')", 'a\\')
+tester("ntpath.join('a', '', '', '', '')", 'a\\')
+
 tester("ntpath.normpath('A//////././//.//B')", r'A\B')
 tester("ntpath.normpath('A/./B')", r'A\B')
 tester("ntpath.normpath('A/foo/../B')", r'A\B')