Make copy of test_mailbox.py. We'll still want to check the backward

compatibility classes in the new mailbox.py that I'll be committing in
a few minutes.

One change has been made: the tests use len(mbox) instead of len(mbox.boxes).
The 'boxes' attribute was never documented and contains some internal state
that seems unlikely to have been useful.

Lib/test/test_old_mailbox.py

+# This set of tests exercises the backward-compatibility class
+# in mailbox.py (the ones without write support).
+
+import mailbox
+import os
+import time
+import unittest
+from test import test_support
+
+# cleanup earlier tests
+try:
+    os.unlink(test_support.TESTFN)
+except os.error:
+    pass
+
+FROM_ = "From some.body@dummy.domain  Sat Jul 24 13:43:35 2004\n"
+DUMMY_MESSAGE = """\
+From: some.body@dummy.domain
+To: me@my.domain
+Subject: Simple Test
+
+This is a dummy message.
+"""
+
+class MaildirTestCase(unittest.TestCase):
+
+    def setUp(self):
+        # create a new maildir mailbox to work with:
+        self._dir = test_support.TESTFN
+        os.mkdir(self._dir)
+        os.mkdir(os.path.join(self._dir, "cur"))
+        os.mkdir(os.path.join(self._dir, "tmp"))
+        os.mkdir(os.path.join(self._dir, "new"))
+        self._counter = 1
+        self._msgfiles = []
+
+    def tearDown(self):
+        map(os.unlink, self._msgfiles)
+        os.rmdir(os.path.join(self._dir, "cur"))
+        os.rmdir(os.path.join(self._dir, "tmp"))
+        os.rmdir(os.path.join(self._dir, "new"))
+        os.rmdir(self._dir)
+
+    def createMessage(self, dir, mbox=False):
+        t = int(time.time() % 1000000)
+        pid = self._counter
+        self._counter += 1
+        filename = os.extsep.join((str(t), str(pid), "myhostname", "mydomain"))
+        tmpname = os.path.join(self._dir, "tmp", filename)
+        newname = os.path.join(self._dir, dir, filename)
+        fp = open(tmpname, "w")
+        self._msgfiles.append(tmpname)
+        if mbox:
+            fp.write(FROM_)
+        fp.write(DUMMY_MESSAGE)
+        fp.close()
+        if hasattr(os, "link"):
+            os.link(tmpname, newname)
+        else:
+            fp = open(newname, "w")
+            fp.write(DUMMY_MESSAGE)
+            fp.close()
+        self._msgfiles.append(newname)
+        return tmpname
+
+    def test_empty_maildir(self):
+        """Test an empty maildir mailbox"""
+        # Test for regression on bug #117490:
+        self.mbox = mailbox.Maildir(test_support.TESTFN)
+        self.assert_(len(self.mbox) == 0)
+        self.assert_(self.mbox.next() is None)
+        self.assert_(self.mbox.next() is None)
+
+    def test_nonempty_maildir_cur(self):
+        self.createMessage("cur")
+        self.mbox = mailbox.Maildir(test_support.TESTFN)
+        self.assert_(len(self.mbox) == 1)
+        self.assert_(self.mbox.next() is not None)
+        self.assert_(self.mbox.next() is None)
+        self.assert_(self.mbox.next() is None)
+
+    def test_nonempty_maildir_new(self):
+        self.createMessage("new")
+        self.mbox = mailbox.Maildir(test_support.TESTFN)
+        self.assert_(len(self.mbox) == 1)
+        self.assert_(self.mbox.next() is not None)
+        self.assert_(self.mbox.next() is None)
+        self.assert_(self.mbox.next() is None)
+
+    def test_nonempty_maildir_both(self):
+        self.createMessage("cur")
+        self.createMessage("new")
+        self.mbox = mailbox.Maildir(test_support.TESTFN)
+        self.assert_(len(self.mbox) == 2)
+        self.assert_(self.mbox.next() is not None)
+        self.assert_(self.mbox.next() is not None)
+        self.assert_(self.mbox.next() is None)
+        self.assert_(self.mbox.next() is None)
+
+    def test_unix_mbox(self):
+        ### should be better!
+        import email.Parser
+        fname = self.createMessage("cur", True)
+        n = 0
+        for msg in mailbox.PortableUnixMailbox(open(fname),
+                                               email.Parser.Parser().parse):
+            n += 1
+            self.assertEqual(msg["subject"], "Simple Test")
+            self.assertEqual(len(str(msg)), len(FROM_)+len(DUMMY_MESSAGE))
+        self.assertEqual(n, 1)
+
+    # XXX We still need more tests!
+
+
+def test_main():
+    test_support.run_unittest(MaildirTestCase)
+
+
+if __name__ == "__main__":
+    test_main()