commerce-8.x-2.8/modules/price/tests/modules/commerce_price_test/commerce_price_test.module

<?php

/**
 * @file
 * Test module for Price.
 */

/**
 * Implements hook_theme().
 */
function commerce_price_test_theme($existing, $type, $theme, $path) {
  return [
    'commerce_price_test' => [
      'template' => 'commerce-price-test-price-filter',
      'variables' => [
        'price' => NULL,
      ],
    ],
  ];
}