ふと OpenBSD で試してみたところ、
test_imaps_post_connection_check が失敗します。

% uname -a
OpenBSD openbsd.tky.aist.go.jp 4.4 GENERIC#1562 amd64
% ./ruby -v test/net/imap/test_imap.rb -n test_imaps_post_connection_check
ruby 1.9.2dev (2009-02-07 trunk 22101) [x86_64-openbsd4.4]
/home/akr/ruby/o0/lib/ruby/1.9.1/x86_64-openbsd4.4/openssl.so: warning: loading in progress, circular require considered harmful - /home/akr/ruby/o0/lib/ruby/1.9.1/openssl.rb
/home/akr/ruby/o0/lib/ruby/1.9.1/openssl.rb:22: warning: loading in progress, circular require considered harmful - /home/akr/ruby/o0/lib/ruby/1.9.1/openssl/ssl.rb
/home/akr/ruby/o0/lib/ruby/1.9.1/openssl/x509.rb:17: warning: loading in progress, circular require considered harmful - /home/akr/ruby/o0/lib/ruby/1.9.1/openssl.rb
Loaded suite test/net/imap/test_imap
Started
F
Finished in 0.004250 seconds.

  1) Failure:
test_imaps_post_connection_check(IMAPTest) [test/net/imap/test_imap.rb:59]:
[OpenSSL::SSL::SSLError] exception expected, not
Class: <Errno::EINVAL>
Message: <"Invalid argument - connect(2)">
---Backtrace---
test/net/imap/test_imap.rb:61:in `new'
test/net/imap/test_imap.rb:61:in `block (2 levels) in test_imaps_post_connection_check'
test/net/imap/test_imap.rb:145:in `imaps_test'
test/net/imap/test_imap.rb:60:in `block in test_imaps_post_connection_check'
test/net/imap/test_imap.rb:59:in `test_imaps_post_connection_check'
---------------

1 tests, 1 assertions, 1 failures, 0 errors, 0 skips

調べてみると、imaps_test で

    server = TCPServer.new(0)

とやって作る TCP サーバが IPv6 専用になっているのに、
test_imaps_post_connection_check 内で

          Net::IMAP.new("127.0.0.1",
                        :port => port,
                        :ssl => { :ca_file => CA_FILE })

と IPv4 な 127.0.0.1 を指定して接続しようとしているからのよ
うです。
-- 
[田中 哲][たなか あきら][Tanaka Akira]