-use_ok 'PublicInbox::V2Writable';
-use_ok 'PublicInbox::Inbox';
-my ($tmpdir, $for_destroy) = tmpdir();
-my $inboxdir = "$tmpdir/inbox";
-my $full = "$tmpdir/inbox/another-nntp.sqlite3";
-my $altid = [ 'serial:gmane:file=another-nntp.sqlite3' ];
+require PublicInbox::Msgmap;
+my $another = 'another-nntp.sqlite3';
+my $altid = [ "serial:gmane:file=$another" ];
+my $ibx = create_inbox 'v2', version => 2, indexlevel => 'medium',
+ altid => $altid, sub {
+ my ($im, $ibx) = @_;
+ my $mm = PublicInbox::Msgmap->new_file("$ibx->{inboxdir}/$another", 2);
+ is($mm->mid_set(1234, 'a@example.com'), 1, 'mid_set') or xbail 'once';
+ is($mm->mid_set(1234, 'a@example.com')+0, 0, 'mid_set not idempotent');
+ is($mm->mid_set(1, 'a@example.com')+0, 0, 'mid_set fails with dup MID');
+ $im->add(PublicInbox::Eml->new(<<'EOF')) or BAIL_OUT;
+From: a@example.com
+To: b@example.com
+Subject: boo!
+Message-ID: <a@example.com>