def METHOD_NAME(cli, project, ext):
    cli.add_project(project.dir, as_lppz=project.is_lppz)
    # remove all boards first
    with open(cli.abspath(project.dir + '/boards/boards.lp'), 'w') as f:
        f.write('(librepcb_boards)')
    relpath_top = project.output_dir + '/pnp/top.' + ext
    relpath_bot = project.output_dir + '/pnp/bot.' + ext
    abspath_top = cli.abspath(relpath_top)
    abspath_bot = cli.abspath(relpath_bot)
    assert not os.path.exists(abspath_top)
    assert not os.path.exists(abspath_bot)
    code, stdout, stderr = cli.run('open-project',
                                   '--export-pnp-top=' + relpath_top,
                                   '--export-pnp-bottom=' + relpath_bot,
                                   project.path)
    assert stderr == ''
    assert stdout == \
        "Open project '{project.path}'...\n" \
        "Export top assembly data to '{project.output_dir}/pnp/top.{ext}'...\n" \
        "Export bottom assembly data to '{project.output_dir}/pnp/bot.{ext}'...\n" \
        "SUCCESS\n".format(project=project, ext=ext)
    assert code == 0
    assert not os.path.exists(abspath_top)  # nothing exported
    assert not os.path.exists(abspath_bot)  # nothing exported