I get this failure in test_mailbox under Windows XP running in a qemu virtual machine:

======================================================================
FAIL: test_reread (test.test_mailbox.TestMaildir)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "Z:\py3k\debug\lib\test\test_mailbox.py", line 764, in test_reread
    assert not refreshed()
AssertionError

----------------------------------------------------------------------

It is reasonably likely that the attached patch will fix this.  It also removes 3 seconds of fixed overhead from the test.

Well, on my new setup (Windows 7 VM with a Python checkout located on an SMB drive), the test sometimes passes and sometimes fails, regardless of the patch.
I suspect that maybe maildir requires atomicity guarantees that a network FS won't provide.

That could be, certainly.  The code is depending on the mtime having a resolution of at least one second.  Try making the constant 61 instead of 60.  If that doesn't work, try putting the mtime back a lot farther and see if that makes it work  If it passes with that change then it could be the assumptions made by the code are also incorrect.

Indeed, 61 seems to work. I don't understand the comment about one-second granularity, shouldn't it be one-minute? (or why do you need 61?)

Hmm.  You are right, I wasn't thinking clearly, and I copied that mtime setting call from another test.  Now I have no idea why 61 would work, unless the clock between your virthost and your smb server is off by a minute?

> Hmm.  You are right, I wasn't thinking clearly, and I copied that
> mtime setting call from another test.  Now I have no idea why 61 would
> work, unless the clock between your virthost and your smb server is
> off by a minute?

No, they seem exactly synchronized.

Could you print out the mtime values that are being set, and the value of self._mbox._last_read?  Or, rather, print out the result of calls to os.path.getmtime on the two directories after the mtime is changed.

before: os.path.getmtime('cur') = 1301075411.6942866
before: os.path.getmtime('new') = 1301075411.693287
after: os.path.getmtime('cur') = 1301075347.38
after: os.path.getmtime('new') = 1301075347.38
self._box._last_read = 1301075407.365
time.time() = 1301075408.395

(the test passed here)

Hmm.  411-61=350.  Three seconds difference looks a little odd.  But doesn't explain 60 vs 61 making the difference in the test.

Can you change it back to 60 (or even less) and see what the values look like when the test fails?

It is interesting (and possibly meaningful) that the last modified time 'before' appears to be in the future compared to time.time by 3-plus seconds.  That would at least explain why the test fails without the patch.

> Hmm.  411-61=350.  Three seconds difference looks a little odd.  But
> doesn't explain 60 vs 61 making the difference in the test.
> 
> Can you change it back to 60 (or even less) and see what the values
> look like when the test fails?

Hmm, 60 doesn't fail anymore so I changed it to 1 (!) and here is the
result:

before: os.path.getmtime('cur') = 1301078411.882165
before: os.path.getmtime('new') = 1301078411.8801715
after: os.path.getmtime('cur') = 1301078410.802999
after: os.path.getmtime('new') = 1301078410.802999
self._box._last_read = 1301078410.787
time.time() = 1301078411.818

(it fails obviously)

> It is interesting (and possibly meaningful) that the last modified
> time 'before' appears to be in the future compared to time.time by
> 3-plus seconds.  That would at least explain why the test fails
> without the patch.

Yep, although the drift is varying. Sometimes small, sometimes big. At
this point I think it's just caused by my setup (the fact that VM and
host aren't always synchronized - I once witnessed time advancing
quicker on the VM than on the host! -, and the fact that a network FS is
used).

All right, so how about I set the add factor to, say, 5, so that if things are mostly in sync it will succeed, and otherwise just ignore your failures :)

New changeset 9a184d8211f5 by R David Murray in branch '3.1':
#9557: eliminate 3 seconds of static overhead from test_mailbox.
http://hg.python.org/cpython/rev/9a184d8211f5

New changeset 268ab32a89a9 by R David Murray in branch '3.2':
Merge #9557: eliminate 3 seconds of static overhead from test_mailbox.
http://hg.python.org/cpython/rev/268ab32a89a9

New changeset 03c7a83bbdd3 by R David Murray in branch 'default':
Merge #9557: eliminate 3 seconds of static overhead from test_mailbox.
http://hg.python.org/cpython/rev/03c7a83bbdd3

Antoine agreed in IRC that this was an acceptable closure.