Issue #2737741 by amateescu, anoopjohn:...

Issue #2737741 by amateescu, anoopjohn: Drupal\menu_link_content\Plugin\Menu\MenuLinkContent::getUuid() does not return any value

core/modules/menu_link_content/src/Plugin/Menu/MenuLinkContent.php

@@ -198,7 +198,7 @@ public function getTranslateRoute() {
    *   The menu link ID.
    */
   protected function getUuid() {
-    $this->getDerivativeId();
+    return $this->getDerivativeId();
   }
 
   /**

core/modules/menu_link_content/tests/src/Unit/MenuLinkPluginTest.php

+<?php
+
+namespace Drupal\Tests\menu_link_content\Unit;
+
+use Drupal\menu_link_content\Plugin\Menu\MenuLinkContent;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\menu_link_content\Plugin\Menu\MenuLinkContent
+ *
+ * @group Menu
+ */
+class MenuLinkPluginTest extends UnitTestCase {
+
+  /**
+   * @covers ::getUuid
+   */
+  public function testGetInstanceReflection() {
+    /** @var \Drupal\menu_link_content\Plugin\Menu\MenuLinkContent $menu_link_content_plugin */
+    $menu_link_content_plugin = $this->prophesize(MenuLinkContent::class);
+    $menu_link_content_plugin->getDerivativeId()->willReturn('test_id');
+    $menu_link_content_plugin = $menu_link_content_plugin->reveal();
+
+    $class = new \ReflectionClass(MenuLinkContent::class);
+    $instance_method = $class->getMethod('getUuid');
+    $instance_method->setAccessible(TRUE);
+
+    $this->assertEquals('test_id', $instance_method->invoke($menu_link_content_plugin));
+  }
+
+}