getPreviewMode example

$form['#attached']['library'][] = 'node/form';

    return $form;
  }

  /** * {@inheritdoc} */
  protected function actions(array $form, FormStateInterface $form_state) {
    $element = parent::actions($form, $form_state);
    $node = $this->entity;
    $preview_mode = $node->type->entity->getPreviewMode();

    $element['submit']['#access'] = $preview_mode != DRUPAL_REQUIRED || $form_state->get('has_been_previewed');

    $element['preview'] = [
      '#type' => 'submit',
      '#access' => $preview_mode != DRUPAL_DISABLED && ($node->access('create') || $node->access('update')),
      '#value' => $this->t('Preview'),
      '#weight' => 20,
      '#submit' => ['::submitForm', '::preview'],
    ];

    

/** * Tests Drupal 6 node type to Drupal 8 migration. */
  public function testNodeType() {
    $id_map = $this->getMigration('d6_node_type')->getIdMap();
    // Test the test_page content type.     $node_type_page = NodeType::load('test_page');
    $this->assertSame('test_page', $node_type_page->id(), 'Node type test_page loaded');
    $this->assertTrue($node_type_page->displaySubmitted());
    $this->assertFalse($node_type_page->shouldCreateNewRevision());
    $this->assertSame(DRUPAL_OPTIONAL, $node_type_page->getPreviewMode());
    $this->assertSame($id_map->lookupDestinationIds(['test_page']), [['test_page']]);

    // Test we have a body field.     $field = FieldConfig::loadByName('node', 'test_page', 'body');
    $this->assertSame('This is the body field label', $field->getLabel(), 'Body field was found.');

    // Test default menus.     $expected_available_menus = ['navigation'];
    $this->assertSame($expected_available_menus, $node_type_page->getThirdPartySetting('menu_ui', 'available_menus'));
    $expected_parent = 'navigation:';
    $this->assertSame($expected_parent, $node_type_page->getThirdPartySetting('menu_ui', 'parent'));

    

'#open' => TRUE,
    ];
    $form['submission']['title_label'] = [
      '#title' => $this->t('Title field label'),
      '#type' => 'textfield',
      '#default_value' => $fields['title']->getLabel(),
      '#required' => TRUE,
    ];
    $form['submission']['preview_mode'] = [
      '#type' => 'radios',
      '#title' => $this->t('Preview before submitting'),
      '#default_value' => $type->getPreviewMode(),
      '#options' => [
        DRUPAL_DISABLED => $this->t('Disabled'),
        DRUPAL_OPTIONAL => $this->t('Optional'),
        DRUPAL_REQUIRED => $this->t('Required'),
      ],
    ];
    $form['submission']['help'] = [
      '#type' => 'textarea',
      '#title' => $this->t('Explanation or submission guidelines'),
      '#default_value' => $type->getHelp(),
      '#description' => $this->t('This text will be displayed at the top of the page when creating or editing content of this type.'),
    ];