subtest "Test some specific postponed merge issues" => sub {

    plan tests => 4;

    my $authmarc = MARC::Record->new;

    $authmarc->append_fields( MARC::Field->new( '109', '', '', 'a' => 'aa', b => 'bb' ));

    my $oldauthmarc = MARC::Record->new;

    $oldauthmarc->append_fields( MARC::Field->new( '112', '', '', c => 'cc' ));

    my $id = AddAuthority( $authmarc, undef, $authtype1 );

    my $biblio = MARC::Record->new;

    $biblio->append_fields(

        MARC::Field->new( '109', '', '', a => 'a1', 9 => $id ),

        MARC::Field->new( '612', '', '', a => 'a2', c => 'cc', 9 => $id+1 ),

        MARC::Field->new( '612', '', '', a => 'a3', 9 => $id+2 ),

    );

    my ( $biblionumber ) = C4::Biblio::AddBiblio( $biblio, '' );

    # Merge A to B postponed, A is deleted (simulated by id+1)

    # This proves the !authtypefrom condition in sub merge

    # Additionally, we test clearing subfield

    merge({ mergefrom => $id + 1, MARCfrom => $oldauthmarc, mergeto => $id, MARCto => $authmarc, biblionumbers => [ $biblionumber ] });

    $biblio = C4::Biblio::GetMarcBiblio( $biblionumber );

    is( $biblio->subfield('609', '9'), $id, '612 moved to 609' );

    is( $biblio->subfield('609', 'c'), undef, '609c cleared correctly' );

    # Merge A to B postponed, delete B immediately (hits B < hits A)

    # This proves the !@record_to test in sub merge

    merge({ mergefrom => $id + 2, mergeto => $id + 1, MARCto => undef, biblionumbers => [ $biblionumber ] });

    $biblio = C4::Biblio::GetMarcBiblio( $biblionumber );

    is( $biblio->field('612'), undef, 'Last 612 must be gone' );

    # Show that we 'need' skip_merge; this example is far-fetched.

    # We *prove* by contradiction.

    # Suppose: Merge A to B postponed, and delete A would merge rightaway.

    # (You would need some special race condition with merge.pl to do so.)

    # The modify merge would be useless after that.

    @linkedrecords = ( $biblionumber );

    my $restored_mocks = set_mocks();

    DelAuthority({ authid => $id }); # delete A

    $restored_mocks->{auth_mod}->unmock_all;

    $biblio = C4::Biblio::GetMarcBiblio( $biblionumber );

    is( $biblio->subfield('109', '9'), $id, 'If the 109 is no longer present, another modify merge would not bring it back' );

};