+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use Test::More;
+use IO::Handle (); # autoflush
+use Fcntl qw(SEEK_SET);
+use PublicInbox::TestCommon;
+require_mods(qw(Compress::Zlib IO::Uncompress::Gunzip));
+require_ok 'PublicInbox::GzipFilter';
+
+{
+ open my $fh, '+>', undef or die "open: $!";
+ open my $dup, '>&', $fh or die "dup $!";
+ $dup->autoflush(1);
+ my $filter = PublicInbox::GzipFilter->new->attach($dup);
+ ok($filter->write("hello"), 'wrote something');
+ ok($filter->write("world"), 'wrote more');
+ $filter->close;
+ seek($fh, 0, SEEK_SET) or die;
+ IO::Uncompress::Gunzip::gunzip($fh => \(my $buf));
+ is($buf, 'helloworld', 'buffer matches');
+}
+
+{
+ pipe(my ($r, $w)) or die "pipe: $!";
+ $w->autoflush(1);
+ close $r or die;
+ my $filter = PublicInbox::GzipFilter->new->attach($w);
+ my $sigpipe;
+ local $SIG{PIPE} = sub { $sigpipe = 1 };
+ open my $fh, '<', 'COPYING' or die "open(COPYING): $!";
+ my $buf = do { local $/; <$fh> };
+ while ($filter->write($buf .= rand)) {}
+ ok($sigpipe, 'got SIGPIPE');
+ close $w;
+}
+done_testing;