class ConfigEntityTest

class ConfigEntityTest extends WebDriverTestBase {
  
  /**
   * {@inheritdoc}
   */
  protected static $modules = [
    'config_test',
  ];
  
  /**
   * {@inheritdoc}
   */
  protected $defaultTheme = 'stark';
  
  /**
   * Tests ajax operations through the UI on 'Add' page.
   */
  public function testAjaxOnAddPage() {
    $this->drupalLogin($this->drupalCreateUser([
      'administer site configuration',
    ]));
    $page = $this->getSession()
      ->getPage();
    $assert_session = $this->assertSession();
    $this->drupalGet('admin/structure/config_test/add');
    // Test that 'size value' field is not show initially, and it is show after
    // selecting value in the 'size' field.
    $this->assertNull($page->findField('size_value'));
    $page->findField('size')
      ->setValue('custom');
    $this->assertNotNull($assert_session->waitForField('size_value'));
  }

}