+#!perl -w
+# 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 v5.10.1;
+use Test::More;
+use PublicInbox::TestCommon;
+use PublicInbox::Eml;
+use PublicInbox::InboxWritable;
+use PublicInbox::Config;
+use List::Util qw(shuffle);
+require_mods(qw(DBD::SQLite));
+require_git(2.6);
+
+chomp(my @msgs = split(/\n\n/, <<'EOF')); # "git log" order
+Subject: [bug#45000] [PATCH 1/9]
+References: <20201202045335.31096-1-j@example.com>
+Message-Id: <20201202045540.31248-1-j@example.com>
+
+Subject: [bug#45000] [PATCH 0/9]
+Message-Id: <20201202045335.31096-1-j@example.com>
+
+Subject: [bug#45000] [PATCH 0/9]
+References: <20201202045335.31096-1-j@example.com>
+Message-ID: <86sg8o1mou.fsf@example.com>
+
+Subject: [bug#45000] [PATCH 8/9]
+Message-Id: <20201202045540.31248-8-j@example.com>
+References: <20201202045540.31248-1-j@example.com>
+
+EOF
+
+my ($home, $for_destroy) = tmpdir();
+local $ENV{HOME} = $home;
+for my $msgs (['orig', reverse @msgs], ['shuffle', shuffle(@msgs)]) {
+ my $desc = shift @$msgs;
+ my $n = "index-cap-$desc";
+ run_script([qw(-init -L basic -V2), $n, "$home/$n",
+ "http://example.com/$n", "$n\@example.com"]) or
+ BAIL_OUT 'init';
+ my $ibx = PublicInbox::Config->new->lookup_name($n);
+ my $im = PublicInbox::InboxWritable->new($ibx)->importer(0);
+ for my $m (@$msgs) {
+ $im->add(PublicInbox::Eml->new("$m\nFrom: x\@example.com\n\n"));
+ }
+ $im->done;
+ my $over = $ibx->over;
+ my @tid = $over->dbh->selectall_array('SELECT DISTINCT(tid) FROM over');
+ is(scalar(@tid), 1, "only one thread initially ($desc)");
+ $over->dbh_close;
+ run_script([qw(-index --reindex --rethread), $ibx->{inboxdir}]) or
+ BAIL_OUT 'rethread';
+ @tid = $over->dbh->selectall_array('SELECT DISTINCT(tid) FROM over');
+ is(scalar(@tid), 1, "only one thread after rethread ($desc)");
+}
+
+done_testing;