public function testFilterEmptyAttribute()
 {
     $filter = new Attribute(new Url('http://google.com'));
     $this->assertTrue($filter->filterEmptyAttribute('abbr', 'title', 'test'));
     $this->assertFalse($filter->filterEmptyAttribute('abbr', 'title', ''));
     $this->assertEquals(array('title' => 'test'), $filter->filter('abbr', array('title' => 'test')));
     $this->assertEquals(array(), $filter->filter('abbr', array('title' => '')));
 }