Issue #3376566 by kunal.sachdev, sakthi_dev, divya.sejekan, Nitin shrivastava,...

<?php

declare(strict_types=1);

namespace Drupal\Tests\system\Functional\Theme;

use Drupal\Tests\node\Functional\NodeTestBase;

/**

 * Tests node title for a theme.

 */

abstract class NodeTitleTestBase extends NodeTestBase {

  /**

   * {@inheritdoc}

   */

  protected $defaultTheme = 'stark';

  /**

   * Modules to enable.

   *

   * @var array

   */

  protected static $modules = ['block'];

  /**

   * {@inheritdoc}

   */

  protected function setUp(): void {

    parent::setUp();

    $this->drupalPlaceBlock('page_title_block');

    $adminUser = $this->drupalCreateUser([

      'administer themes',

      'administer nodes',

      'create article content',

      'create page content',

    ]);

    $this->drupalLogin($adminUser);

  }

  /**

   * Get the theme name.

   *

   * @return string

   *   The theme to test.

   */

  protected function getTheme(): string {

    return explode('\\', get_class($this))[2];

  }

  /**

   * Creates one node with title 0 and tests if the node title has the correct value.

   */

  public function testNodeWithTitle0(): void {

    $theme = $this->getTheme();

    if ($theme !== $this->defaultTheme) {

      $system_theme_config = $this->container->get('config.factory')

        ->getEditable('system.theme');

      $system_theme_config

        ->set('default', $theme)

        ->save();

      \Drupal::service('theme_installer')->install([$theme]);

    }

    // Create "Basic page" content with title 0.

    $settings = [

      'title' => 0,

    ];

    $node = $this->drupalCreateNode($settings);

    // Test that 0 appears as <title>.

    $this->drupalGet('node/' . $node->id());

    $this->assertSession()->titleEquals('0 | Drupal');

    // Test that 0 appears in the template <h1>.

    $this->assertSession()->elementTextEquals('xpath', '//h1', '0');

  }

}

<?php

declare(strict_types=1);

namespace Drupal\Tests\claro\Functional;

use Drupal\Tests\system\Functional\Theme\NodeTitleTestBase;

/**

 * Tests node title for claro.

 *

 * @group node

 */

class NodeTitleTest extends NodeTitleTestBase {

}

%}

{{ title_prefix }}

{% if title|render|striptags|trim %}

{% if (title|render|striptags|trim is not empty) %}

  <h1{{ title_attributes.addClass(classes) }}>{{ title }}</h1>

{% endif %}

{{ title_suffix }}

<?php

declare(strict_types=1);

namespace Drupal\Tests\olivero\Functional;

use Drupal\Tests\system\Functional\Theme\NodeTitleTestBase;

/**

 * Tests node title for olivero.

 *

 * @group node

 */

class NodeTitleTest extends NodeTitleTestBase {

}