Tests: check pipelining after invalid command.

smtp.t

diff --git a/smtp.t b/smtp.t
index 06165a5..bd2d4c7 100644
--- a/smtp.t
+++ b/smtp.t
@@ -9,7 +9,7 @@
 use warnings;
 use strict;
 
-use Test::More tests => 24;
+use Test::More tests => 25;
 
 use IO::Socket;
 use MIME::Base64;
@@ -55,6 +55,11 @@
 TODO: {
 	local $TODO = "pipelining not implemented yet";
 
+	smtp_send('INVALID COMMAND WITH ARGUMENTS' . CRLF
+		. 'RSET');
+	smtp_read();
+	smtp_ok('rset after invalid command');
+
 	smtp_send('AUTH PLAIN '
 		. encode_base64("test\@example.com\0\0bad", '') . CRLF
 		. 'MAIL FROM:<test@example.com> SIZE=100');