[PATCH] t/imap_searchqp: hopefully fix test reliability

[Eric Wong <e@80x24.org>]

Localizing assignments to *STDERR doesn't seem to always work
with scalar (String) IO objects.  Fortunately, doing actual dup2
redirects always seems reliable, so do that instead of
attempting to understand why PerlIO sometimes fails with the
assignment.
---
 t/imap_searchqp.t | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/t/imap_searchqp.t b/t/imap_searchqp.t
index ff1b4535..d7840dd0 100644
--- a/t/imap_searchqp.t
+++ b/t/imap_searchqp.t
@@ -3,6 +3,8 @@
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
 use v5.10.1;
+use autodie qw(open seek read);
+use Fcntl qw(SEEK_SET);
 use Time::Local qw(timegm);
 use PublicInbox::TestCommon;
 require_mods(qw(-imapd));
@@ -29,12 +31,15 @@ is($q->{xap}, 'f:"b"', 'charset handled');
 $q = $parse->(qq{CHARSET WTF-8 From b});
 like($q, qr/\ANO \[/, 'bad charset rejected');
 
-for my $x ('', ' (try #2)') {
-	open my $fh, '>:scalar', \(my $buf = '') or die;
-	local *STDERR = $fh;
+{
+	open my $tmperr, '+>', undef;
+	open my $olderr, '>&', \*STDERR;
+	open STDERR, '>&', $tmperr;
 	$q = $parse->(qq{CHARSET});
-	last if is($buf, '', "nothing spewed to STDERR on bad query$x");
-	diag 'FIXME: above fails mysteriously sometimes, so we try again...';
+	open STDERR, '>&', $olderr;
+	seek $tmperr, 0, SEEK_SET;
+	read($tmperr, my $buf, -s $tmperr);
+	is($buf, '', 'nothing spewed to STDERR on bad query');
 }
 
 like($q, qr/\ABAD /, 'bad charset rejected');