/**
  * @covers WPSEO_OpenGraph::article_author_facebook
  */
 public function test_article_author_facebook()
 {
     // test not on singular page
     $this->assertFalse(self::$class_instance->article_author_facebook());
     // create post with author
     $author_id = $this->factory->user->create(array('role' => 'administrator'));
     $post_id = $this->factory->post->create(array('post_author' => $author_id));
     $this->go_to(get_permalink($post_id));
     // on post page but facebook meta not set.
     $this->assertFalse(self::$class_instance->article_author_facebook());
     // add facebook meta to post author
     $post = get_post($post_id);
     $author = $post->post_author;
     add_user_meta($author, 'facebook', 'facebook_author');
     // test final output
     $this->assertTrue(self::$class_instance->article_author_facebook());
     $this->expectOutput('<meta property="article:author" content="facebook_author" />' . "\n");
 }