ZF2 phpUnit test view helper

Unfortunatelly i'm absolute zero in ZF2 and unit testing. I wrote simple view helper(wrapper function of Zend Translate) and now i have to write a test for this. I'm trying to add one test in existing test class, so everything is configured ...maybe. I simply need to get to work this code:

public function testTranslation()
{
    $result = $this->t('about');
    $expected = "About";
    $this->assertEquals($exp, $res);
}

I also tried to get functionality like i do it in controllers, but no luck:

$t = $this->getServiceLocator()->get('ViewHelperManager')->get('t');
$result = $t('about');

Any help ?