Module imaplib has pretty sparse test code.  There is only 1 test case,
for imaplib.Time2Internaldate.
trunk/Lib/test/test_imaplib.py

The attached patch tests for LF, CR preservation with regard to the
IMAP4.append method, but more testing is necessary to make sure LF, CR
are preserved in IMAP literals throughout imaplib and that the
respective fix doesn't break anything.  Mock IMAP interaction may be the
way to go for better test cases.  Is anyone working on expanding imaplib
test coverage?

-Ron