public function testPointerIteration()
 {
     $this->assertEquals($this->_0, $this->collection->next());
     $this->assertEquals($this->_1, $this->collection->next());
     $this->assertEquals($this->_2, $this->collection->next());
     $this->assertEquals($this->_3, $this->collection->next());
     $this->assertEquals(null, $this->collection->next());
     $this->assertEquals($this->_3, $this->collection->previous());
     $this->assertEquals($this->_2, $this->collection->previous());
     $this->assertEquals($this->_1, $this->collection->previous());
     $this->assertEquals($this->_0, $this->collection->previous());
     $this->assertEquals(null, $this->collection->previous());
     $this->collection->setPointer(2);
     $this->assertEquals($this->_2, $this->collection->current());
 }