only in patch2:
unchanged:
--- /dev/null
+++ b/tests/src/FunctionalJavascript/LayoutBuilderDisplayVariantTest.php
@@ -0,0 +1,115 @@
+<?php
+
+namespace Drupal\Tests\page_manager\FunctionalJavascript;
+
+use Drupal\FunctionalJavascriptTests\WebDriverTestBase;
+use Drupal\Tests\contextual\FunctionalJavascript\ContextualLinkClickTrait;
+use Drupal\Tests\user\Traits\UserCreationTrait;
+
+/**
+ * Test the layout_builder variant plugin.
+ *
+ * @group page_manager
+ */
+class LayoutBuilderDisplayVariantTest extends WebDriverTestBase {
+
+  use UserCreationTrait;
+  use ContextualLinkClickTrait;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected static $modules = [
+    'layout_builder',
+    'page_manager_ui',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+
+    $this->drupalLogin($this->createUser(array_keys($this->container->get('user.permissions')
+      ->getPermissions())));
+  }
+
+  /**
+   * Tests the layout builder variant.
+   */
+  public function testLayoutBuilderVariant() {
+    $this->drupalGet('admin/structure/page_manager/add');
+    $page = $this->getSession()->getPage();
+    $assert_session = $this->assertSession();
+
+    $page->fillField('label', 'Example');
+    $assert_session->waitForElementVisible('css', '.machine-name-value');
+    $this->submitForm([
+      'path' => '/example',
+      'variant_plugin_id' => 'layout_builder',
+    ], t('Next'));
+
+    $this->submitForm([
+      'page_variant_label' => 'Layout Builder',
+    ], t('Next'));
+
+    // Add a two column section.
+    $this->clickLink('Add Section');
+    $assert_session->waitForElementVisible('named', ['link', 'One column']);
+    $this->clickLink('Two column');
+    $assert_session->assertWaitOnAjaxRequest();
+    $page->pressButton('Add section');
+    $assert_session->assertWaitOnAjaxRequest();
+
+    // Place a block in the first region.
+    $page->find('css', '.layout__region--first .layout-builder__link--add')
+      ->click();
+    $page->clickLink('Add Block');
+    $assert_session->assertWaitOnAjaxRequest();
+    $this->clickLink('Powered by Drupal');
+    $assert_session->assertWaitOnAjaxRequest();
+    $page->pressButton('Add Block');
+    $assert_session->assertWaitOnAjaxRequest();
+    $assert_session->pageTextContains('Powered by Drupal');
+
+    // Test content preview.
+    $page->uncheckField('toggle_content_preview');
+    $this->assertNotEmpty($assert_session->waitForElementVisible('css', '.layout-builder-block__content-preview-placeholder-label'));
+
+    $page->pressButton('Finish');
+    $assert_session->pageTextContains('The layout has been saved.');
+
+    // Go the layout builder variant.
+    $this->drupalGet('admin/structure/page_manager/manage/example/page_variant__example-layout_builder-0__layout_builder');
+
+    // Place another block in the first region.
+    $page->find('css', '.layout__region--first .layout-builder__link--add')
+      ->click();
+    $page->clickLink('Add Block');
+    $assert_session->assertWaitOnAjaxRequest();
+    $this->clickLink('User account menu');
+    $assert_session->assertWaitOnAjaxRequest();
+    $page->pressButton('Add Block');
+    $assert_session->assertWaitOnAjaxRequest();
+    $assert_session->pageTextContains('User account menu');
+
+    // Test drag and drop.
+    $page->find('css', '.layout__region--first .menu--account')
+      ->dragTo($page->find('css', '.layout__region--second'));
+    $assert_session->assertWaitOnAjaxRequest();
+
+    // Test contextual links.
+    $assert_session->waitForElement('css', '.block-system-powered-by-block .contextual');
+    $this->clickContextualLink('.block-system-powered-by-block', 'Configure');
+    $this->assertNotEmpty($assert_session->waitForElementVisible('css', '#drupal-off-canvas'));
+
+    // Save page.
+    $page->pressButton('Update and save');
+
+    // Check if block is rendered in the correct region.
+    $this->drupalGet('example');
+    $assert_session->elementExists('css', '.layout__region--first .block-system-powered-by-block');
+    $assert_session->elementExists('css', '.layout__region--second .block-menu.menu--account');
+  }
+
+}