Tests: add missing rewrite prerequisite.
diff --git a/mail_smtp_xclient.t b/mail_smtp_xclient.t
index 4da0753..2fd6ebf 100644
--- a/mail_smtp_xclient.t
+++ b/mail_smtp_xclient.t
@@ -25,7 +25,7 @@
 
 local $SIG{PIPE} = 'IGNORE';
 
-my $t = Test::Nginx->new()->has(qw/mail smtp http/)->plan(6)
+my $t = Test::Nginx->new()->has(qw/mail smtp http rewrite/)->plan(6)
 	->run_daemon(\&Test::Nginx::SMTP::smtp_test_daemon)
 	->write_file_expand('nginx.conf', <<'EOF')->run();