public function testSlice()
 {
     $this->collection[] = 'one';
     $this->collection[] = 'two';
     $this->collection[] = 'three';
     $slice = $this->collection->slice(0, 1);
     $this->assertInternalType('array', $slice);
     $this->assertEquals(array('one'), $slice);
     $slice = $this->collection->slice(1);
     $this->assertEquals(array(1 => 'two', 2 => 'three'), $slice);
     $slice = $this->collection->slice(1, 1);
     $this->assertEquals(array(1 => 'two'), $slice);
 }