Issue #2944089 by msankhala, smustgrave, lauriii, Ada Hernandez, TanujJain-TJ,...

<?php

namespace Drupal\system_test\Form;

use Drupal\Core\Form\FormBase;

use Drupal\Core\Form\FormStateInterface;

/**

 * Provides a form to test Drupal.behaviors.copyFieldValue.

 */

class CopyFieldValueTestForm extends FormBase {

  /**

   * {@inheritdoc}

   */

  public function getFormId() {

    return 'copy_field_value_test_form';

  }

  /**

   * {@inheritdoc}

   */

  public function buildForm(array $form, FormStateInterface $form_state) {

    $form['#attached']['library'][] = 'system/drupal.system';

    $form['#attached']['drupalSettings']['copyFieldValue']['edit-source-field'] = ['edit-target-field'];

    $form['source_field'] = [

      '#type' => 'textfield',

      '#title' => $this->t('Source Field'),

      '#default_value' => '',

      '#description' => $this->t('Source input field to provide text value.'),

      '#required' => TRUE,

    ];

    $form['target_field'] = [

      '#type' => 'textfield',

      '#title' => $this->t('Target Field'),

      '#default_value' => '',

      '#description' => $this->t('Target input field to get value from source field.'),

      '#required' => TRUE,

    ];

    return $form;

  }

  /**

   * {@inheritdoc}

   */

  public function submitForm(array &$form, FormStateInterface $form_state) {

    // We are only testing the JavaScript part of form. We are not submitting

    // form.

  }

}

  requirements:

    _access: 'TRUE'

system_test.copy_field_value:

  path: '/system-test/copy-field-value-test-form'

  defaults:

    _form: '\Drupal\system_test\Form\CopyFieldValueTestForm'

    _title: 'Copy Field Value Test Form'

  requirements:

    _access: 'TRUE'

system_test.install_profile:

  path: '/system-test/get-install-profile'

  defaults:

<?php

namespace Drupal\Tests\system\FunctionalJavascript;

use Drupal\FunctionalJavascriptTests\WebDriverTestBase;

/**

 * Tests copy field value functionality.

 *

 * @see Drupal.behaviors.copyFieldValue.

 *

 * @group system

 */

class CopyFieldValueTest extends WebDriverTestBase {

  /**

   * {@inheritdoc}

   */

  protected static $modules = ['system_test'];

  /**

   * {@inheritdoc}

   */

  protected $defaultTheme = 'starterkit_theme';

  /**

   * Tests copy field value JavaScript functionality.

   */

  public function testCopyFieldValue() {

    $this->drupalGet('/system-test/copy-field-value-test-form');

    $page = $this->getSession()->getPage();

    $source_field_selector = 'edit-source-field';

    $target_field = $page->find('css', '#edit-target-field');

    $random_string = $this->randomString();

    // Ensure that after source field has been filled, target field is filled

    // with the same value.

    $page->fillField($source_field_selector, $random_string);

    $target_field->focus();

    $this->assertEquals($target_field->getValue(), $random_string);

    // Ensure that the target value doesn't change after it has been focused.

    $page->fillField($source_field_selector, '');

    $target_field->focus();

    $this->assertEquals($target_field->getValue(), $random_string);

  }

}