--- /dev/null
+<?php
+
+namespace Drupal\Tests\layout_builder\Functional\Update;
+
+use Drupal\Core\Entity\Entity\EntityViewDisplay;
+use Drupal\FunctionalTests\Update\UpdatePathTestBase;
+
+/**
+ * Tests the upgrade path for Layout Builder extra fields.
+ *
+ * @group layout_builder
+ * @group legacy
+ */
+class ExtraFieldUpdatePathTest extends UpdatePathTestBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ protected function setDatabaseDumpFiles() {
+ $this->databaseDumpFiles = [
+ __DIR__ . '/../../../../../system/tests/fixtures/update/drupal-8.4.0.bare.standard.php.gz',
+ __DIR__ . '/../../../fixtures/update/layout-builder.php',
+ __DIR__ . '/../../../fixtures/update/layout-builder-extra.php',
+ ];
+ }
+
+ /**
+ * Tests the upgrade path for Layout Builder extra fields.
+ */
+ public function testRunUpdates() {
+ // The default view mode has Layout Builder enabled.
+ $data = EntityViewDisplay::load('node.article.default')->toArray();
+ $this->assertArrayHasKey('third_party_settings', $data);
+ $this->assertArrayNotHasKey('sections', $data['third_party_settings']['layout_builder']);
+
+ // The teaser view mode does not have Layout Builder enabled.
+ $data = EntityViewDisplay::load('node.article.teaser')->toArray();
+ $this->assertArrayNotHasKey('third_party_settings', $data);
+
+ $this->runUpdates();
+
+ // The extra links have been added.
+ $data = EntityViewDisplay::load('node.article.default')->toArray();
+ $components = $data['third_party_settings']['layout_builder']['sections'][0]->getComponents();
+ $component = reset($components);
+ $this->assertSame('extra_field_block:node:article:links', $component->getPluginId());
+
+ // No extra links have been added.
+ $data = EntityViewDisplay::load('node.article.teaser')->toArray();
+ $this->assertArrayNotHasKey('third_party_settings', $data);
+ }
+
+}