DiDom\Element::firstChild PHP Method

    public function firstChild()
    {
        if ($this->node->firstChild === null) {
            return null;
        }
        return new Element($this->node->firstChild);
    }

 public function testFirstChild()
 {
     $html = '<ul><li>One</li><li>Two</li><li>Three</li></ul>';
     $document = new Document($html, false);
     $list = $document->first('ul');
     $this->assertEquals($list->getNode()->firstChild, $list->firstChild()->getNode());
     $list = new Element('ul');
     $this->assertNull($list->firstChild());
     // with text nodes
     $html = '<p>Foo <span>Bar</span> Baz</p>';
     $document = new Document($html, false);
     $paragraph = $document->first('p');
     $firstChild = $paragraph->getNode()->firstChild;
     $this->assertEquals($firstChild, $paragraph->firstChild()->getNode());
 }