--- /dev/null
+<?php
+
+namespace Drupal\FunctionalJavascriptTests\Core\Form;
+
+use Drupal\FunctionalJavascriptTests\JavascriptTestBase;
+
+/**
+ * Tests for form grouping elements.
+ *
+ * @group form
+ */
+class FormGroupingElementsTest extends JavascriptTestBase {
+
+ /**
+ * Required modules.
+ *
+ * @var array
+ */
+ public static $modules = ['form_test'];
+
+ /**
+ * {@inheritdoc}
+ */
+ protected function setUp() {
+ parent::setUp();
+
+ $account = $this->drupalCreateUser();
+ $this->drupalLogin($account);
+ }
+
+ /**
+ * Tests that vertical tab children become visible.
+ *
+ * Makes sure that a child element of a vertical tab that is not visible,
+ * becomes visible when the tab is clicked, a fragment link to the child is
+ * clicked or when the URI fragment pointing to that child changes.
+ */
+ public function testVerticalTabChildVisibility() {
+ $session = $this->getSession();
+ $web_assert = $this->assertSession();
+
+ // Request the group vertical tabs testing page with a fragment identifier
+ // to the second element.
+ $this->drupalGet('form-test/group-vertical-tabs', ['fragment' => 'edit-element-2']);
+
+ $page = $session->getPage();
+
+ $tab_link_1 = $page->find('css', '.vertical-tabs__menu-item > a');
+
+ $child_1_selector = '#edit-element';
+ $child_1 = $page->find('css', $child_1_selector);
+
+ $child_2_selector = '#edit-element-2';
+ $child_2 = $page->find('css', $child_2_selector);
+
+ // Assert that the child in the second vertical tab becomes visible.
+ // It should be visible after initial load due to the fragment in the URI.
+ $this->assertTrue($child_2->isVisible(), 'Child 2 is visible due to a URI fragment');
+
+ // Click on a fragment link pointing to an invisible child inside an
+ // inactive vertical tab.
+ $session->executeScript("jQuery('<a href=\"$child_1_selector\"></a>').insertAfter('h1')[0].click()");
+
+ // Assert that the child in the first vertical tab becomes visible.
+ $web_assert->waitForElementVisible('css', $child_1_selector, 50);
+
+ // Trigger a URI fragment change (hashchange) to show the second vertical
+ // tab again.
+ $session->executeScript("location.replace('$child_2_selector')");
+
+ // Assert that the child in the second vertical tab becomes visible again.
+ $web_assert->waitForElementVisible('css', $child_2_selector, 50);
+
+ $tab_link_1->click();
+
+ // Assert that the child in the first vertical tab is visible again after
+ // a click on the first tab.
+ $this->assertTrue($child_1->isVisible(), 'Child 1 is visible after clicking the parent tab');
+ }
+
+ /**
+ * Tests that details element children become visible.
+ *
+ * Makes sure that a child element of a details element that is not visible,
+ * becomes visible when a fragment link to the child is clicked or when the
+ * URI fragment pointing to that child changes.
+ */
+ public function testDetailsChildVisibility() {
+ $session = $this->getSession();
+ $web_assert = $this->assertSession();
+
+ // Store reusable JavaScript code to remove the current URI fragment and
+ // close all details.
+ $reset_js = "location.replace('#'); jQuery('details').removeAttr('open')";
+
+ // Request the group details testing page.
+ $this->drupalGet('form-test/group-details');
+
+ $page = $session->getPage();
+
+ $session->executeScript($reset_js);
+
+ $child_selector = '#edit-element';
+ $child = $page->find('css', $child_selector);
+
+ // Assert that the child is not visible.
+ $this->assertFalse($child->isVisible(), 'Child is not visible');
+
+ // Trigger a URI fragment change (hashchange) to open all parent details
+ // elements of the child.
+ $session->executeScript("location.replace('$child_selector')");
+
+ // Assert that the child becomes visible again after a hash change.
+ $web_assert->waitForElementVisible('css', $child_selector, 50);
+
+ $session->executeScript($reset_js);
+
+ // Click on a fragment link pointing to an invisible child inside a closed
+ // details element.
+ $session->executeScript("jQuery('<a href=\"$child_selector\"></a>').insertAfter('h1')[0].click()");
+
+ // Assert that the child is visible again after a fragment link click.
+ $web_assert->waitForElementVisible('css', $child_selector, 50);
+
+ // Find the summary belonging to the closest details element.
+ $summary = $page->find('css', '#edit-meta > summary');
+
+ // Assert that both aria-expanded and aria-pressed are true.
+ $this->assertTrue($summary->getAttribute('aria-expanded'));
+ $this->assertTrue($summary->getAttribute('aria-pressed'));
+ }
+
+}