selectTextInsideElement example

    $original_value = $this->host->body->value;
    $this->host->body->value = str_replace('data-caption=""', 'data-caption="baz"', $original_value);
    $this->host->save();
    $this->drupalGet($this->host->toUrl('edit-form'));
    $this->waitForEditor();
    $this->assertNotEmpty($assert_session->waitForElementVisible('css', '.ck-widget.drupal-media img'));
    $this->assertNotEmpty($figcaption = $assert_session->waitForElement('css', '.drupal-media figcaption'));
    $this->assertSame('baz', $figcaption->getHtml());

    // Ensure that the media contextual toolbar is visible when figcaption is     // selected.     $this->selectTextInsideElement('.drupal-media figcaption');
    $this->assertVisibleBalloon('[aria-label="Drupal Media toolbar"]');
    $expected_buttons = [
      'Toggle caption off',
      'Link media',
      'Override media image alternative text',
      // Check only one of the element style buttons since that is sufficient       // for confirming that element style buttons are visible in the toolbar.       'Break text',
    ];
    foreach ($expected_buttons as $expected_button) {
      $this->assertNotEmpty($this->getBalloonButton($expected_button));
    }

    // Set a taller window size to ensure all possible style choices are in view     // because otherwise Mink's getText() will return the empty string for those     // out of view, despite the HTML showing that text.     $this->getSession()->resizeWindow(1024, 1000);

    $this->drupalGet($node->toUrl('edit-form'));
    $this->waitForEditor();

    // Select the <h2>, assert that no style is active currently.     $this->selectTextInsideElement('h2');
    $assert_session = $this->assertSession();
    $style_dropdown = $assert_session->elementExists('css', '.ck-style-dropdown');
    $this->assertSame('Styles', $style_dropdown->getText());

    // Click the dropdown, check the available styles.     $style_dropdown->click();
    $buttons = $style_dropdown->findAll('css', '.ck-dropdown__panel button');
    $this->assertCount(9, $buttons);

    $this->assertSame('Highlighted & interesting', $buttons[0]->find('css', '.ck-button__label')->getText());
    $this->assertSame('Red heading', $buttons[1]->find('css', '.ck-button__label')->getText());