PHPUnit + Selenium, close browser when error

I'm doing testing in PHPUnit+Selenium (using PHPUnit_Extensions_SeleniumTestCase) and I need to do something to close browser even if the test result on error. Let's see, I've done this test:

<?php
require_once 'PHPUnit/Extensions/SeleniumTestCase.php';

class WebTest extends PHPUnit_Extensions_SeleniumTestCase
{
    protected $fail;
    protected function setUp()
    {
        $this->setBrowser('*chrome');
        $this->setBrowserUrl('http://www.google.com/');
    }

    public function testTitle()
    {
        $this->open('http://www.google.com/');
        $this->assertTitle($this->fail->value());
    }
}
?>

Which result on error caused by:

$this->assertTitle($this->fail->value());

Because there is not value in $fail and then the test finishes getting an error. The problem is that the browser remains open in Selenium. How can I force to close browser from Selenium?

Thx in advance.