fix: #3526541 Cannot set default values on multi-valued formatted Text fields

        'default_value_input',

        $field_name,

      ]);

      // Remove the 'add_more' button from the submitted values if it exists.

      if (isset($submitted_values['add_more'])) {

        unset($submitted_values['add_more']);

      }

      foreach ($submitted_values as $delta => $value) {

        if (!in_array($value['format'], $allowed_formats, TRUE)) {

          $form_state->setErrorByName(

<?php

declare(strict_types=1);

namespace Drupal\Tests\text\Unit\Plugin\Field\FieldType;

use Drupal\Core\Field\FieldDefinitionInterface;

use Drupal\Core\Form\FormStateInterface;

use Drupal\Core\StringTranslation\TranslatableMarkup;

use Drupal\Tests\UnitTestCase;

use Drupal\text\Plugin\Field\FieldType\TextFieldItemList;

/**

 * Tests TextFieldItemList.

 *

 * @coversClass \Drupal\text\Plugin\Field\FieldType\TextFieldItemList

 * @group text

 */

class TextFieldItemListTest extends UnitTestCase {

  /**

   * Tests ::defaultValuesFormValidate() if the field allows multiple values.

   *

   * Ensures that the add_more button is filtered out of the submitted values

   * before validation, preventing PHP warnings due to trying to access array

   * keys on a TranslatableMarkup object.

   */

  public function testDefaultValuesFormValidateWithMultipleCardinality(): void {

    $field_name = 'field_test_text';

    $definition = $this->createMock(FieldDefinitionInterface::class);

    $definition->expects($this->once())

      ->method('getName')

      ->willReturn($field_name);

    $definition->expects($this->once())

      ->method('getSetting')

      ->with('allowed_formats')

      ->willReturn(['restricted_html']);

    $form_state = $this->createMock(FormStateInterface::class);

    $form_state->expects($this->once())

      ->method('getValue')

      ->with(['default_value_input', $field_name])

      ->willReturn([

        'add_more' => new TranslatableMarkup('Add another item'),

      ]);

    $form_state->expects($this->once())

      ->method('has')

      ->with('default_value_widget')

      ->willReturn(TRUE);

    $form_state->expects($this->once())

      ->method('get')

      ->with('default_value_widget')

      ->willReturn([]);

    $item_list = new TextFieldItemList($definition);

    $form = [];

    $item_list->defaultValuesFormValidate([], $form, $form_state);

  }

}