set list on;

    set term ^;
    create or alter procedure sp_cleanup as
    begin
        begin
            execute statement 'drop user tmp_4766_boss using plugin %(current_auth_plugin)s' with autonomous transaction;
            when any do begin end
        end
     
        begin
        execute statement 'drop user tmp_4766_mngr using plugin %(current_auth_plugin)s' with autonomous transaction;
            when any do begin end
        end
    end
    ^
    set term ;^
    commit;

    -- removed 27.01.2020 because unneeded for this test:
    -- select mon$user,mon$remote_protocol,mon$auth_method from mon$attachments where mon$attachment_id=current_connection;
    -- commit;

    execute procedure sp_cleanup;
    commit;

    create user tmp_4766_boss password '123' using plugin %(current_auth_plugin)s grant admin role;
    commit;
    
    select u.sec$user_name boss_sec_name, u.sec$plugin boss_sec_plugin, u.sec$admin boss_sec_is_admin
    from rdb$database r
    left join sec$users u on u.sec$user_name = upper('tmp_4766_boss');

    set term ^;
    execute block as
    begin
        execute statement 'create user tmp_4766_mngr password ''456'' using plugin %(current_auth_plugin)s'
        as user 'tmp_4766_boss' password '123' role 'RDB$ADMIN';
    end
    ^
    set term ;^
    commit;

    set bail on;
    rollback; -- Crash is reproduced here, WI-T3.0.0.31374 Firebird 3.0 Beta 1 (build 24-nov-2014).
    set bail off;
    
    select u.sec$user_name mngr_sec_name, u.sec$plugin mngr_sec_plugin, u.sec$admin mngr_sec_is_admin
    from rdb$database r
    left join sec$users u on u.sec$user_name = upper('tmp_4766_mngr');

    set term ^;
    execute block as
    begin
        execute statement 'drop user tmp_4766_mngr using plugin %(current_auth_plugin)s'
        as user 'tmp_4766_boss' password '123' role 'RDB$ADMIN';
    end
    ^
    set term ;^
    commit;

    rollback; -- otherwise "rolling back work", despite that COMMIT was done just now, see previous line !

    execute procedure sp_cleanup;
    commit;