TQ\Vcs\Buffer\ArrayBuffer::key PHP Method

    public function key()
    {
        return key($this->array);
    }

 public function testIteration()
 {
     $listing = array('a', 'b', 'c');
     $iterator = new ArrayBuffer($listing);
     $i = 0;
     while ($iterator->valid()) {
         $this->assertEquals($listing[$i], $iterator->current());
         $this->assertEquals($i, $iterator->key());
         $i++;
         $iterator->next();
     }
     $this->assertEquals(count($listing), $i);
     $iterator->rewind();
     $this->assertEquals(reset($listing), $iterator->current());
     $this->assertEquals(key($listing), $iterator->key());
 }