public function test()
 {
     $tag = new Tag();
     $this->assertEquals('<div></div>', $tag->render());
     $tag->setTagName('a');
     $this->assertEquals('<a></a>', $tag->render());
     $tag->setAttributes(['class' => 'btn']);
     $this->assertEquals('<a class="btn"></a>', $tag->render());
     $first = new Tag();
     $first->setTagName('i')->setAttributes(['class' => 'icon']);
     $first->children()->add(new DataView('&nbsp;'));
     $second = new DataView('Hi!');
     $tag->children()->set([$first, $second]);
     $this->assertEquals('<a class="btn"><i class="icon">&nbsp;</i>Hi!</a>', $tag->render());
 }