example-pattern.config.php

<?php 

return [
    'props' => [
        'title' => [
            'type'     => 'field',
            'required' => true,
        ],
        'links' => [
            'type'     => 'structure',
            'required' => true
        ],
        'modifier' => [
            'type'     => 'string',
            'default'  => 'Example--dark',
            'validator => function($value) {
                return v::in($value, ['Example--dark', 'Example--light']);
            }
        ]
    ]
]

example-pattern.html.php

<div class="ExamplePattern <?= $modifier ?>">
    <h2><?= $title->html() ?></h2>
    
    <ul>
        <?php foreach ($links as $link) ?>
        <li><a href="<?= $link->url() ?>"><?= $link->text() ?></a></li>
        <?php endforeach ?>    
    </ul>
</div>

example-pattern.test.php

<?php 

class ExamplePatternTest extends TestCase
{
    protected $fixtures = __DIR__ . '/_fixtures';

    public function testExample()
    {

        $page = page('some-page/from/fixtures');

        $dom = $this->patternDom('example-pattern', [
            'title'    => $page->title(),
            'links'    => $page->links()
            'modifier' => 'Example--light',
        ]);

    }

}

example-template.php

<?php snippet('header') ?>

<?php pattern('example-pattern', [
    'title'    => $page->title(),
    'links'    => $page->links()
    'modifier' => 'Example--light',
]) ?>

<?php snippet('footer') ?>