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)); } }